I don't enjoy having sex with my boyfriend. Need some advice.

My (21M) boyfriend (23M) and I have been in a relationship since about 1 month. We only see each other on weekend although he lives quite close from my apartment because we must pay attention to study. He's nice to me but the problem is that mostly every time we had sex, he's on top and after he "finishes", he doesn't care that I haven't and goes to sleep directly. I really feel uncomfortable, even angry. I think that having sex has to be a mutual enjoyment, right? Do you guys have any advice for this situation because it makes me sometimes really want to break up with him despite his kindness? Have a good day!