What martial art should I learn?

I'm 13 years old and I've always loved to fight! I'm not a bad kid, its just that I like to deliver pain (and get some of it back). Me amd my brother like to have fake kickboxing matches and things like that. The UFC has always been an inspiration to me! I'm 4'6", roughly 90 lbs., and in pretty good shape. I wanna learn Brazilian Jiu-Jitsu, Muay Thai, and Taekowdo! Which should I learn?