I know what it feels like to be treated like a toy and not as a partner.....if he won't hear you, you have a decision to make.
How much of this are you willing to take?? In my experience if they are selfish, they won't listen, they won't change. I hope you can resolve it.
My advice would be to do directly. Politely, and be understanding. He may not have any idea, especially if he's young. It's also possible he's a jerk, but I'm not in the mood to assume that everybody's a total wanker today, so I'll advise you assuming that he's not. He may also not know very much about your anatomy and how to stimulate it. Let him know that he can ask questions, and you shouldn't be embarrassed about answering them. Show him what you like and what you want. Also, point out some things that really don't work for you, so that he knows you have boundaries, and what they are, and that he didn't cause you to wince or squirm away because he's bad at something. Also beware, he will probably not be very good at doing the things you want at first, and there will be some that he's not into, at least at first. Make the learning experience a good one. Fun for both of you.
If on the other hand, he shows no interest in learning about your body, your pleasure and your needs, that is evidence pointing to the 'he's a jerk theory'. Anyway, I hope one or both of those pieces of advice help.
From a mans perspective I would simply let him find you taking matters in your own hands and when he tried to squeeze in tell him if he would do his part you to would be satisfied . Maybe it will make him jealous. Sounds like he hasn't taken time to find out what makes you happy. Age could be a factor.
Tell exactly what you've told us. That's a start in the right direction. In addition, teach him. Teach him how to please you, and if he's unwilling to listen and learn, then he's unworthy of your love and body.