How to get you and a friend to start humping each other?

So I am currently 14 and a male. Every Tuesday my friend and I get together. No one thinks of me as a perv or anything. I'm always thought of as very innocent. Whenever I hang out with my friend we tackle each other and do some rough play. It never gets sexual, but I always get turned on whenever we do this. I have always had the urge to hump him whenever I tackle him and have always wanted him to do the same to me. For some reason I am attracted to his slight chubbiness and his butt. I've always wanted to especially hump his butt. I always am attracted to chubby males my age with large butts (I don't know why, is this normal?). I have been imagining him humping me and me doing the same to him and want it to happen really bad, but just don't have the courage to. I don't want to be seen as a perv though. I just don't have the courage to actually hump him. How can I possibly get this to happen? I know he would accept this because he has humped me a little, but not for real. He is a big perv too. This is also weird, but sometimes, he sticks his butt out at me still with his clothes on and farts in my face and I enjoy it. I don't know of it is normal to enjoy something like this, but I enjoy it very much. Whenever this happens, I am tempted to either hump his butt or put my face in it. Is this normal? Anyways, I guess my main question is: if I know my friend will enjoy and accept this, how can I start humping him and having him do the same to me? Also, am I gay? I know t is perfectly fine if i am, but I also find interest in females.