I need motivation to get up and change myself.

I've always been larger—mainly due to genetics. I truly don't eat that much but I do enjoy eating. I am 230 lbs and I'm in 8th grade. I am really smart and in many advanced classes but I feel like I cannot do shit about being this way. I want to lose the weight because it makes me feel horrible, but I don't have the motivation to get up, and I don't know where to start. I can't go to the gym because memberships here are crazy expensive and my ankle is broken. I feel useless in my own body. Is there anything I can do to lose it?