Only the previous week, Samantha had found out we'd been secretly using her place for our masturbation group – and that her little brother had organised it. Instead of freaking out, though, she'd ended up joining us and had even helped Tiff and I to buy our first vibrators.

Every session started off with solo play. It was during that part when Samantha made an announcement. 'Tiff and me, we're now a couple.'

'What?' I said. 'That's insane. You only met a week ago.'

'You’ve seen us. We go well together. Oh, and we can still do stuff with people in the group, that's allowed.'

I still had my new vibrator switched on, but I'd lost the orgasmic build-up. 'That's still really fast.'

Steven and Jack sat close together watching from the other side of the room. Jack let out an, 'Ew,' as his sister leaned over to kiss Tiff.

'What's that meant to mean?’ said Samantha. 'You've literally watched us having sex.'

'I didn't watch.'

'I did,' added Steven.

As the siblings traded insults, I watched our newest addition still stroking himself. This was Thomas, who'd been part of the original group at school. I'd asked some of the others to continue our sessions, but only Tiff, Steven, and Jack had agreed. I'd never thought to ask Thomas at the time because he had a lot of trouble orgasming and I didn't think he'd enjoy it. When Samantha had joined us, however, it had turned our four members into five and I'd felt like the odd one out.

I heard Jack say, 'Well, me and Steven are a couple as well.'

We all looked at him, including Steven, none of us sure how to take the news.

'No you're not,' I said eventually, 'you always say you're just experimenting.'

'No, we're a couple,’ he said snippily, ‘have been for weeks, months.'

'That's not what you've been telling us,' said Samantha.

'No, it's not,' said Steven. He turned to the rest of us, 'This is news to me as well.' We nodded to show we understood.

'Yeah, we talked about, it remember?' he said to Steven.

'No.'

'You said you wanted to be boyfriends?'

'And you said, flat out, "No-no-no, this is just a bit of fun," and we were just experimenting, and we’d never be boyfriends.'

'Well, we're a couple,' interrupted Jack.

'So we're boyfriends now?'

'Yes, of course, we are.'

‘It's a bit sudden, don’t you think?’

‘Do you want to be a couple or not?’

‘I want to be asked first.’

Samantha interrupted by throwing a carrier bag next to them. ‘I got all this for you when I bought the vibrators.’

Steven put his hand in the bag. ‘Condoms? And lube?’

‘I know you have sex. Why don’t you just do it here? You already go ninety percent of the way.’

The discussion continued for some time. It took ages before everyone was naked and the masturbation turned into group play. The boys started touching and stroking each other, and the girls cuddled in together, running their hands over each other's boobs.

Prompted by this, I moved over to Thomas, who was still stroking away furiously, and I masturbated in front of him, making sure he could see me clearly. With my free hand, I ran my fingers down his chest. We'd all talked to him in detail beforehand about what we’d done in the group up until then, but he still seemed nervous and it took him a while to relax.

We reached a stage where he was holding my vibrator against me while I stroked him. I'd learnt the technique that I found worked for the other boys: to make my finger and thumb into a tight circle, then pull the foreskin back and forth over the ridge at the base of the head. When they were close to spurting, I'd put my lips over the top to catch and swallow it. I knew that would take a while with him. Meanwhile, guiding him gently, he hit my sweet spot and I was able to climax twice.

The girlfriends were still all over each other, but it was the boyfriends who took most of my attention. They kept looking at what Samantha had bought and whispering to each other. It was then that I realised what was about to happen. I couldn't believe I would ever watch two boys having sex in the same room, but here we were. They’d clearly done this many times before: Jack rolled on a condom onto himself with ease, and Steven was already lubricating himself.

Before I knew what I was doing, I'd grabbed another condom from the bag and began to roll it onto Thomas as I kissed him. He knew what was going to happen and he didn't complain, despite his nerves. Once we’d kissed a bit more, I moved beside Steven and copied his position, on his hands and knees, gesturing for Thomas to go behind me.

Thomas slowly pushed into my vagina. It felt a little bit sore as I stretched at first, but God, it felt good when he got into a rhythm. I'll be honest, I'd always imagined losing my virginity in a bedroom with lots of candles around me, but this was just as good.

Before long, I watched Jack as he slowed down his thrusts and it was clear he'd finished inside his new boyfriend. He took off his condom, then he tried to hand in to me.

'What are you doing?'

'I thought you liked swallowing?'

'Not out of... that thing. Throw it out.'

I turned my attention back to the female side of the room. The previous week, Samantha had shown us her couples' vibrator, and now she was using it: one end inside her and the other thrusting in and out of Tiff. But whereas internal pleasure worked for Tiff, I needed my clit touched, so Thomas thrusting into me wouldn't get me off by itself.

I rested on one arm and reached for my vibrator again as he kept going. He kept apologising that he was taking so long, but I had no complaints: he stayed hard and kept his rhythm up. He was also noticeably longer and thicker than the other two.

I'd expected the boys to swap places afterwards, so Steven would enter Jack, but they didn't. Instead, they cuddled up to each other. Meanwhile, the girls came to a natural break and stopped to have a drink.

'Sorry,' said Thomas for the hundredth time, 'it's fine when I'm on my own.'

'Honestly,' I said once again, 'it's great.'

Tiff came over. 'Thomas? Why don't you come and do it with me?' She lay on her back beside me. 'And Steven, you can take Thomas's place.'

'One minute,' I said, making adjustments to my vibrator, 'I just need to...' and then it started to build up, my third orgasm. Normally, that's too much for me at once, but I was so turned on.

After that, Thomas stopped his strokes, then slowly pulled out and moved over to Tiff, who guided him inside her. Steven was still hard. He put on a condom and entered me from behind in the same way. He had a different rhythm from Thomas, but it was just as nice. The only thing spoiling it was Jack being clingy again, with his hands all over Steven. Samantha eventually told him to leave us in peace.

Steven didn't leave me long enough to reach a fourth orgasm. Oddly enough, Tiff and Thomas didn't take long either, both orgasming within a few minutes. Maybe he just needed different stimulation.

We'd been meeting up as a group for at least a year. In school, we were sixteen and turning seventeen, and now we were about to turn eighteen and would soon be off to college. Samantha was also turning twenty-one, although she wasn't going anywhere and would happily let us continue using her place for as long as we were around.

On our eighteenth birthdays, we were allowed to choose something special to do, as long as the other group members agreed.

Steven was the first – and he wanted a threesome with me and Tiff. It was a predictable request, but I enjoyed it. I kept 90% of my touching with him rather than her, and it culminated in him alternating with having sex with Tiff for one minute, then me for one minute, until he finally finished inside her. The others watched us and occasionally touched us.

This started a domino effect.

Jack asked for an all-male threesome. Thomas wasn't keen at first because he'd never done anything gay before, but he agreed to join them. That then prompted Samantha to ask for an all-female session. It wouldn't have been my first choice, but I said I would take part.

It made sense to have the two threesomes on the same day instead of one side of the room sitting watching the other. Unfortunately, the siblings' birthdays were three months apart, so Samantha ended up doing it weeks after her birthday, while Jack was able to have his long before.

On the day, both our groups went through similar phases of fingering each other, then oral. Even Thomas looked as though he was having a good time. Then we moved on to penetration. On our side, we took turns with the couples' vibrator. On their side, only Jack penetrated Steven, although both were running their hands all over Thomas and kissing him.

Then it was the turn of Tiff and Thomas to have their treats. She wasn't shy about saying what she wanted: she'd seen anal sex so many times and wanted to feel it for herself. Thomas, on the other hand, needed to be coaxed, until he finally admitted he'd wanted to receive anal as well, but had been too shy to try it during the threesome.

Again, it made sense to have the two on the same day. Steven went behind Tiff, who was on her hands and knees. Next to them, Jack was behind Thomas. The boyfriends kissed and touched each other throughout. Neither Tiff nor Thomas seemed to like it at first, but they both said they enjoyed it once the pain subsided.

When it was my turn to choose, I was tempted to ask for another threesome, this time with Steven and Thomas, but as I'd already had that experience, I decided on something different. I asked instead if I could swallow all the boys' semen at the same time. The plan was for them all to masturbate together, letting Thomas finish first because he would take longest, then the other two would add theirs shortly afterwards.

It worked perfectly because the boyfriends had practiced orgasming at the same time. Thomas ejaculated into Steven's hand, then the other two did. There was more of the stuff than I'd ever seen in one place. He carefully emptied it into my mouth and I got a thrill from knowing I was tasting all of them at once. I then licked his hand clean and kissed all the boys on the cheek, even Jack.

Up to that point, I'd managed to be part of the group every single time we met. My streak was about to be broken, though, and that was because my parents were planning a holiday around my birthday. We never went abroad: it was always somewhere like a log cabin or a chalet, and this year I was going to spend seven days in a static caravan with them and my little brother.

Outside of the group, I was still giving myself at least one orgasm a day, so I'd need to be sneaky. Still, there were ways to do it even when you were stuck with family all the time.