I just wanted to say to everyone else here that you might be too hard on him. What's so simple to you is not so simple to someone else! Of course it's only logical to not do something that you don't like, so then obviously something else is going on. I may be gullible to be believing this kid but I'd rather believe and offer advice, than not believe and cause him more trouble.
Now to address the OP, I don't want to pretend that I know exactly what you're going through, but I did have my own experience with such things.
When I was about 16, I started having sex with strangers, men. I am not attracted to men. but I did it. and it totally grossed me out and I wanted to throw up the whole time I was doing it. So why would I do that? I still don't really know. It was a time in my life when I was really suicidal, and I literally didn't care about my life, I didn't care if I got an STD or if I got pregnant. I had sex almost because it was just something to do. A part of it did make me feel good about my body. I liked that somebody liked my body, I could pretend in that moment that they liked me. Even though I knew I was just fooling myself.
I didn't even want to stop. I really still don't fully understand how or why I kept doing it.
The only thing that got me to stop is when I moved about and was in a better environment and wasn't suicidal anymore.
Now, I don't want to assume anything about you. But I do suspect that your home life is not the best environment with the way you talk about your parents. So maybe, is there a way to get into a better place? Do you have group trans or LGBT mettings in your area? I only say trans or LGBT, not because this is related to you being trans, but because these are examples of environments with really supportive, loving people. Maybe you could even talk to a school counselor about all your feelings and she could direct you to supportive environments in your area?