How can I lose weight?

I'm 13 years old and 5'9. I used to do alot of modeling but ... here's my story. At the beginning of the last school year I only weighed 115 but I began picking up weight quick but my doctor just said it was puberty. But the problem was I'm a basketball player, cheerleader, and gymnast and I was gaining weight on top of all the practices and Athletics(not the same as p.e.) cl. Well at the end of the school year I then weighed 140. Now it's 2 months later and I'm almost 150! I hate my weight! My mom has been calling me fat since I started to pick up weight and I just tried to ignore it. But within this past week I noticed I really am getting big and it's not muscle! I guess i should have noticed I was getting to big when my cheer coach said I could no longer be a flyer because it was a strain on the bases. How can I lose weight? I want to be a flyer and model again!!!