Adivce!?! PLEASE HELPPP!!!!!?

Let's just say Im kinda chubby. I'm 5' 6" 13 years old, and about 150 pounds. I'm not really fat, considering im really strong for a girl, and musle wieghs more than fat.. diets and stuff wont help.. does anyone know where i can get one of those things that tuck in your stomach? Other advice would help alot too..