Wednesday morning came in a flash. I quickly showered and shaved, grabbed an energy bar, and ran out the door. I was late.

I practically sprinted down the halls to Dr. Hu's office, bursting through the door, hoping she wouldn't scold me, which she does often as if she were my mother.

"Why are you panting so heavily, Ben?" The doctor asked. She stood by the one window in the room, which looked out over a small courtyard.

"I was running late," I said, catching my breath. "I'm sorry, I woke up late, and..."

"It's okay, Ben. I don't need the whole story. I'm just glad you're here. Have a seat." She gestured to the chair at her desk as she approached from the window.

Sheri Hu was a very beautiful woman for her age. She was petite and kept herself in great shape, as I found out when I ran into her at the program's fitness center two weeks ago. Before that, I had only seen her in the white lab coat she wore to work every day. In gym clothes, however, her shapely figure was very much on display. She had a firm, toned butt, and an ample chest that her sports bra had difficulty hiding. Being of Chinese descent meant her facial features did well to hide her true age, with soft, smooth skin, high cheekbones, and thin, almond eyes. It was shortly after I started the program that I ran into her at the gym, and was only mildly attracted to her, as anyone three decades younger would be, mostly impressed by her ability to stay in shape. But in the present, as Dr. Hu rounded her desk to sit across from me, I could make out the subtle hint of her curves and something stirred inside me. My cock started getting hard.

"As we discussed, you'll be given three more weekly injections, starting today. These will be unlike the first three, as they are more potent," she said, sitting.

"More potent?" I raised an eyebrow.

"Yes. You see, as your body changes due to the treatments, it requires stronger doses to achieve the results I'm after."

"And what are the results you're after?" I asked, eyebrow still raised and cock growing harder. I couldn't help thinking what her tits looked like under her lab coat.

"Again, as we discussed, there's higher demand, Ben. You do understand what that means?"

I thought for a moment. Demand, in this case, would be for more pregnancies.

"I think you mean more girls are signing up, right?"

"That's correct," she smiled. "Now how do you suppose we keep up with demand without having more donors enlisting, hmm?"

"Gosh, I dunno. Maybe have us work more sessions?" I offered.

"No. That wouldn't do. You would be fully spent by the second session in a day. Try again," Dr. Hu said, now leaning back in the chair, with a sly smirk on her face. She knew I was stumped.

"I give up, okay. Just tell me," I pleaded, weakly. My erection had subsided now that I was taking this a bit more seriously.

"My aim is for you to go three or maybe even four sessions in one day, but that will be down the road. The treatment will do the work to your body, but your mind needs work, too. That's where Sandra comes in."

"Whoa, wait a minute." I stood up and paced the room, pondering the doctor's words. "Four sessions in one day? That's, like, sixteen girls!"

"I know it's hard to fathom, Ben, but I promise you, you will be more than capable. For the time being, however, you'll be limited to one session a day, twice a week. You'll need to focus on controlling your body, with Sandra's help, of course."

"Okay, I'm a little confused. I'm still not sure why Sandra has to be involved. I mean, I think she's great and all, but is it necessary? What exactly is she going to be doing?"

"Well, until you both get an understanding of the effects of the extra treatments, it's really up to the two of you. I will be here to help if you need it, but I think you'll be just fine."

"Well, that doesn't help," I said, plopping back down in the chair.

"Don't get too comfortable. I have other donors to see. Follow me to the exam room next door."

Dr. Hu led me to a small, neighboring room which was your typical exam room. Instead of having me sit on the exam table, she had me sit in a chair against the wall and lift my shirt.

"Okay, Ben, this will feel no different than the others. Just a little poke in the belly," she said, producing a small syringe from the tray beside her.

She punctured my right side, about halfway between my belly button and my crotch. It didn't hurt any more than the prior injections, producing a minor, dull ache. The doctor put a small bandaid over the injection site.

"There you go, nothing to it. Now listen, Ben, you will feel some uncomfortable pain, not unlike your prior injections, though perhaps slightly more intense. If, for any reason, you experience very sharp pain, nausea, or vomiting, call me immediately. Any questions?"

"When will my next session be?" I asked.

"Ah, yes. I almost forgot. Wednesday will be your next session, 11 a.m. You'll need to rest today and Sandra will see you tomorrow night, as I've instructed her to begin coaching you then."

"Okay, that's it, then. I'll see you in a couple days."

"Yes. Let me give you one suggestion before you go." Dr. Hu then walked up and stood uncomfortably close to me. She grabbed my junk and said, "Try to make the last one, the best one."

Dr. Hu's advice stuck with me the whole bus ride home. I had no clue what she meant by it. What I did know was the treatment was kicking in, much sooner than the previous doses. I felt an ache in my lower abdomen and a slight stabbing pain in my scrotum. Luckily, it did not get any worse as the day went on. I obeyed Dr. Hu and lazed around the house, watching a couple of movies and napping twice. I was awoken from my second nap to a call on my wall screen. It was Sandra.

"Hey, how's it going? How was your treatment?" Sandra asked when her face appeared on the screen. She looked more beautiful to me, her skin was glowing on the high-definition screen.

"Good, I suppose. It's made me tired, and a little sore. But I suppose that was to be expected. How are you? You look radiant," I said, not sure how she would take the compliment from a coworker.

"Oh, really? That's very nice of you, but I think your screen must have a filter on it or something." We both laughed.

"No, no filter," I said.

"Okay, then." She smiled. "So, what did Dr. Hu tell you?"

"Not much. Just that we need to work together to help me achieve the impossible."

"Yeah, that's pretty much what I got out of her, too. I gotta say, I'm a bit nervous. I don't have the slightest clue as to how to help. Well, not that I'm helpless or anything, but I'm not sure what the outcome of this should be. Does that make sense?" she asked.

"Totally! I agree. I mean, she said her goal is for me to go three or four sessions a day! I don't know how anyone could possibly do that?"

"Hold on, she said what? Three or four sessions a day!?" Sandra's mouth was agape. "Ben, she told me her goal was to have you cum in as many as ten girls in one session."

"Are you serious? That's insane! There's no way in hell I could do that! She's out of her mind."

I sat upright on the edge of my bed and pondered the situation. I had no idea what Dr. Hu was thinking, but the more I thought about it and thought of having Sandra help me, whatever that meant, the more I was intrigued.

"Listen, I'm still up to try whatever it is Dr. Hu has in mind for us. What are your thoughts?"

After a long pause, Sandra spoke, "Truth is, I like you, Ben. I'm very much attracted to you, but I don't want that to get in the way of our work. I'll help, but we have to be professional about it."

"Oh, I understand, totally," I smiled, my excitement obvious. "I really like you, too. I promise to keep it professional. So when do we start?"

"We can start tomorrow. I have some errands to run in the morning, so after lunch would be okay."

"Perfect. How about two o'clock, my place?"

"See you then, take care," Sandra smiled and waved, then disconnected.

I exhaled and was shocked to realize I was fully erect, sitting on the edge of my bed in just my underwear. I was accustomed to Sandra seeing me practically naked, since she was there to see that everything was in order before I began each depositing session, but being on a private call like that and her possibly seeing me with a raging boner was rather embarrassing. I crossed my fingers, hoping that part was hidden off-screen.

My stomach was a wreck of nerves and anxiety as the night went on. The aching in my nether regions persisted, becoming an afterthought by the time I finally hit the sack. I slept like a rock.

I awoke Thursday at 11:00 a.m., several hours past normal. I would be home from the gym and showered already. The aching I felt the previous day was gone, however, it was replaced with a tingling in my testicles and the base of my penis. I went to the bathroom and, while I expected to see my balls had grown, I  was not prepared for the amount in which they had. After my previous injection, weeks ago, my nutsack felt like it had two golf balls inside. Now, my testes were almost as big as pool balls, stretching the skin fairly tight. My dick looked like it had grown some, which was expected, though the full effects of the treatment wouldn't be seen for another day or two.

I hit the gym, late, to do upper-body workouts, then went home to shower. As I lathered myself, I couldn't help but caress and stroke myself, admiring my big cock and balls. I wondered what Sandra would think when she saw them. She never did make any mention of my junk at work, which was most professional of her, but I wondered if she ever thought about me after hours. I was getting hard thinking about it. I let myself cool off and finished my shower, heading to the kitchen for my usual protein shake when my wall screen next to the sink came on, a voice call from Sandra.

"Hey Sandra," I answered.

"Hi, Ben. Would it be okay if I came a little early? I'm not far from you now, and I'd rather not go all the way back home."

I looked at the time and realized it was already 1:30 p.m.

"Sure", I said, looking down at my naked self, chuckling, "I'm just hanging out."

"Um, okay. I'll be there in about five minutes. See you then." The call disconnected.

I didn't have time for a shake and ran to my room to throw on some clothes. I grabbed a pair of gym shorts and a tank top, opting to forego underwear. The door chime sounded moments later.

"Wow, that was quick. You must have been really close," I said as Sandra stepped through the doorway into my apartment. She looked amazing in street clothes, only wearing a purple sports bra and tight, black gym shorts. I was used to seeing her in her work uniform, which hid her athletic figure. She was roughly five-nine, and rail thin, but with subtle curves in the right places. Her sports bra squeezed her smallish boobs just enough to form a hint of cleavage. Sandra brushed her long blonde hair over her shoulder and hugged me. I hoped she didn't feel my growing erection against her thigh.

"Yeah, I was just around the corner getting some makeup from that new store, Lush."

"Oh, right. They just opened, I think."

"Last week. I wanted to get some of their mascara, I've heard it's great."

"I wouldn't know anything about it," I laughed. "So, anyway, welcome to my apartment."

"Thanks. It's nice," Sandra said. We both stood silent for an awkward moment.

"Well, how should we begin?" I asked.

"Hmm, I'm not sure." Sandra's demeanor quickly changed, her face showing real seriousness. "I suppose, firstly, we need to get you into an aroused state, just like you would be heading into a session?"

I tried to get myself into the same frame of mind, though it was hard with Sandra here helping, wearing what I deemed a sexy outfit. I was only accustomed to the help of the priming device before a session.

"I agree, though I think that would best be achieved by a primer. We don't have that luxury here," I said. We both thought for a moment and then the spark of an idea flashed on Sandra's beautiful face.

"I can try to simulate the primer," she said, shrugging her shoulders. "Would you be okay with that?"

I tried to hide my excitement and be professional, but failed.

"Of course I would! I mean, yes, that would be okay, if it's what you think would be most helpful."

"The primer's main function is to keep you in a state of arousal to help increase sperm production. I'll try to replicate that, and for the full fifteen minutes, just like before a session. Take your clothes off."

I enjoyed how direct Sandra's instructions were, and I did as I was told, removing my tank top and shorts. My cock was at half-mast, clearly bigger than it was just the day prior.

"My goodness, Ben," Sandra practically gasped. "I knew the treatments caused some growth down there, but holy shit."

She stared wide-eyed at my cock as it slowly grew. I watched her eyes dart between it and my balls.

"Dr. Hu's expectations seemed crazy, but with those balls, I think you could get twenty girls pregnant." Sandra laughed and cupped one of my swollen-looking nuts in her hand.

"Yeah, it's kind of crazy how this all works, and it happens so quickly."

"Interesting! Is there any pain?" she asked, softly caressing my sack.

"It's not bad, really only lasts a day. This time was a little worse, but judging by how much size I gained it makes sense."

We both watched as my dick grew to its full length, sticking out a good ten inches or more from my crotch.

"God, it's huge," Sandra said quietly, but still loud enough for me to hear. "Okay, back to business. So the primer will keep you hard and stimulated, but not to the point of giving you an orgasm. This way, when you begin a session, you won't be wasting unnecessary time getting to that point. That's our first goal."

Sandra began stroking my cock, slowly and rhythmically. It felt amazing, having a woman's hand on my penis, something I hadn't felt in months. As much as I wanted to concentrate on this being a simulation of the primer, it wasn't working. Having a woman right here with me, a beautiful one at that, doing the work manually was clouding my thoughts. I was imagining Sandra with her top off, her cute, perky tits out for me to grope. Her lips were big and soft, begging to be kissed. It's true, I was fucking girls at work regularly, but I missed the intimacy of real sex. I missed the foreplay; the touching and kissing, sucking and licking.

"I don't know if this is going to work, Sandra," I said, truthfully. "It feels too good, and I can't stop thinking about you."

"What do you mean?" she asked.

"I haven't been intimate with anyone in a long time. I know I shouldn't think of it like that, but it's just that I think you're really hot and, well, it's turning me on too much."

"I see."

I expected her to stop stroking me, but she didn't. Instead, she drooled a big glob of spit onto her palm and worked it over my cock, lubing it up and down.

"That's only going to make you a better donor, Ben. This is all about control. If you can learn to keep those thoughts at bay, you'll be able to succeed in Dr. Hu's plan."

She quickened her pace, stroking my full length, occasionally working my glans. I focused on clearing my mind of any sexual thoughts. I closed my eyes as Sandra lubed me up with more of her saliva. She was stroking me with a rhythm that felt, surprisingly, much like the primer.

"Just like that," I told her.

For a couple of minutes, she glided her hand up and down my hard member. I succeeded at keeping my head clear, and the sensations I was feeling diminished. I had no concept of time, and when I snapped out of my ultra-relaxed state, I was surprised to see, and feel, Sandra kneeling, bobbing her head up and down on my cock. She looked up and saw me watching her.

"You learn quickly," she said, after taking me out of her mouth. "It's been a good twenty minutes. I couldn't help myself, your cock looks so good. And my wrists were getting tired," she laughed.

"You should know, last session, I found I was able to control my ejaculations. I'm not really sure how I did it, but I tried to get in that same headspace."

"Well, you're doing something right to go that long without cumming." Sandra was still stroking me slowly. "And that leads to our second goal, which if you say you can control your ejaculations, we shouldn't have a problem with. Let's say there's four girls here, you'll have to cum in each one," Sandra said.

"That's easy. But I like to give the girls a little extra something for their participation."

"Oh, and what's that?" she asked, intrigued.

"I like to give each girl at least one orgasm."

"Wait, so you actually fuck each one until they cum, before you cum?"

"Yeah, why? Is that wrong of me?" I gave a little pouty face.

"No, not at all," she shook her head. "It's just not how I imagined it at all. I thought you fucked the first girl until you came, then quickly deposited it into each girl."

"Oh, like I only came once?"

"Yeah."

"Nope. At least that's not how I do it. I can't say how other donors do it. They don't let us talk to one another. I couldn't even tell you who the other donors are."

"That's crazy. I need to see this for myself." Sandra was back at stroking my cock, which was pretty well lubed up from her suck job. "So you can cum more than once if I keep jerking you off?"

"I think so. Again, this is kinda new to me, doing it like this. I can't guarantee anything."

"Alright, let's see what you got."

Sandra then engulfed my engorged cock head with her mouth, sucking and slurping while stroking me hard and fast. I let myself become attuned to the sensations, bringing me closer to the edge of orgasm. Sandra tried deep-throating me, but gagged a little and withdrew me from her mouth, gasping. Just as she did, my first orgasm hit me like a crashing wave.

"Oh, shit," she exclaimed as a massive, thick rope of cum splashed off her face and neck. It was followed by five or six more, each just as big as the first. She managed to aim my pulsing cock lower, a huge load of cum first ricocheting off of her chin, then coating her neck and chest. A few, smaller spurts ended the barrage, splashing down on her bare thighs.

"I'm sorry, I should have warned you I was gonna cum," I said, reaching for my shirt for Sandra to wipe the globs of semen off of her beautiful face.

"Um, yeah," she said. "That was a pretty powerful orgasm. But it's okay, at least you didn't get any in my eyes." She chuckled as she cleaned herself off.

"You look pretty hot right now," I said, smiling and stroking myself back to fully erect.

"Oh, come on now, I must look ridiculous with all your cum on me. And that's not very professional of you," she gave me a rather sexy evil eye.

Sandra tossed my cum soaked shirt to the side and placed her hand around my cock, above my own. We both stroked in unison, our eyes locked on one another's.

"Let's see what you got for round two," she said, then took me in her warm mouth.

I removed my hand and let her suck and stroke me. After a few minutes, she began massaging my balls, causing me to moan with pleasure. It was almost too much, and I had to try to reign myself in.

I focused on Sandra's hand stroking my shaft, and the way she synchronized it with her head movement. My concentration became so deep that I could no longer feel any of it, I only watched her expertly sucking me off, as if it was in slow motion. The way her hand twisted with each upstroke, in time with her lips gliding over the edge of my glans. Then her hand slid back down to the base, her lips following behind, half of my cock buried in her mouth. I could feel her tongue sensually massaging my frenulum, occasionally circling the tip of my engorged cock head.

As much as I tried to hold off an orgasm, I could feel it building. My focus slipped and I felt my cock twitch in Sandra's mouth. She must have felt it, too, and pulled me out of her mouth. My concentration snapped.

"Are you gonna cum for me?" she asked in a sexy voice, stroking me and looking into my eyes.

All I could do was nod my head.

I held back as long as I could before I felt the incredible pressure in my balls let loose. Sandra was ready this time and aimed my throbbing cock at her tits. My cock exploded with pleasure, sending a flurry of cum rockets splashing off of Sandra's sports bra. It was almost completely covered in jizz from just that first volley, but I wasn't nearly done, as this orgasm was more intense than the first.  I felt another surge from my balls, up my cock shaft, and plastered her chest once more with a good half-dozen, huge ropes of cum.

"My god, that's a lot of cum," Sandra said in amazement, looking down at her cum-covered chest.

I had a few more small spurts of cum left, which splashed onto her stomach and laced her shorts.

"It is a lot, isn't it?" I said. "My last orgasm usually has the most."

"You're joking, right? You mean to tell me if you cum again it will be more than this?" Sandra said, gesturing to show the mess her upper body was currently covered in.

"No, I'm not joking," I said matter-of-factly.

"Well, in some sense that's actually great. You'll need all that cum if you're gonna deposit it into ten willing pussies."

Sandra then used two fingers to gather up some of my thick cum and licked them clean. Her expression was one of surprise.

"Ben, your cum is delicious," she said, like she had just tasted ice cream for the first time.

"I'm glad you like it, but that's very professional," I reminded her.

"Fuck professional," she said, gathering up more cum and eating it. "I need more of it."

Without hesitation, Sandra began sucking me once more, my cock only half-hard. It didn't take long for it to get rock-hard. She sucked my dick fanatically, slobbering and spitting all over it, determined to induce my next orgasm as quickly as possible. I had other ideas, though. I wanted to give her what she wanted, and that was more cum.

For what felt like an hour, but was really only ten minutes due to my intense focus, Sandra sucked and stroked me. She spent some time sucking on and licking my huge balls. Her effort paid off when my third orgasm hit. This time, I tried to gain control of my body and my ejaculations.

I grabbed the back of Sandra's head and held it in place so that just the head of my cock was in her mouth. My attempt at controlling my muscles didn't work so well at first, as I pumped about eight massive spurts of hot cum into her mouth. It must have filled her up too fast because she gagged a little bit and spit some out around my cock before being able to swallow it. I managed to relax my pelvic floor muscles enough to pump one long stream of cum into her mouth. She was able to swallow this one easily. My mind was acutely focused on filling Sandra's mouth with one big shot of cum at a time, timing it so she could swallow before I pumped her mouth full again. Not that I was counting, but I must have filled her with seven or eight mouthfuls of cum, each one she swallowed like a champion. The last few I let go in one big load, and she swallowed, moaning.

Sandra pulled me out with a much-needed gasp.

"Fuck, that was incredible!" she yelled with excitement.

"You said you liked the taste. It was good, then?"

"Was it ever!? Were you controlling it? Like, the way you would cum, then I'd swallow, then you'd fill me up again. The timing was perfect. That first one, though, I almost lost it," she giggled.

"Yeah, sorry about that."

"No, no. I still liked it. I'm not gonna lie, I've never had a guy cum in my mouth. Actually, I've never liked the taste of cum before."

"Really? I would have never guessed," I said, chuckling.

Sandra licked my cock, cleaning the head as a few drops of cum still leaked out.

"I don't know about you, but I'm exhausted," Sandra said, her breathing labored.

"Well, you have done a lot of work. And believe me, all that cumming is exhausting, too," I sighed.

"I bet it is." Sandra let my now flaccid cock hang free. "Here's what I'm thinking, Ben. For you to impregnate as many girls as Dr. Hu wants, you'll need to be able to do what you did that last time, every time."

"I know, it's not easy though."

"I get it, but I know you can do it. Also, in order for us to train properly I think we need it to be more like the real deal."

"What do you mean?" I asked, perplexed.

"I mean, you need to make a real deposit," Sandra said, using air quotes on the last word.

"Oh, you mean cum inside you?" I had a look of concern on my face.

"Yes, silly. You'll have to cum in my pussy."

"But...hold on a min..."

"It's okay, Ben. Don't worry about getting me pregnant. I can't, anyway," Sandra said, heading toward the door.

"Really? I had no idea," I said, following her.

"It really is okay. Besides, isn't it fun knowing you can cum in me as many times as you want and not have to worry about it?"

Sandra kissed me on the cheek, then walked out of my apartment, in her cum-stained purple sports bra.

"I'll be back tomorrow. Same time," she said, sauntering off down the walkway.

K