I knew a guy who only liked anal sex (with women) and years later he came out of the closet and admitted he was gay. Hope that isn't what is going on for your guy.
well ,, you could try taking the lead. taking control for a night. be your inner sexy and do different things that makes him and YOU especially feel good .
I believe that he should not push you and if he does I would probably think about getting out of the relationship. I believe that you are too young to worry about that kind of thing. I told my daughter to not worry about relationships until she was out of school and was on the career path she wants. I think you would be better off not being with him. If you insist on being with this person please make sure you use protection because having anal sex can be very dangerous. Please take care of yourself, you are special and important and you do not need to be worrying about things like that at your age. I will keep you in my prayers.
Jackie