How to stop eating so much junk food?

Hi im 14 and in eighth grade. And I weigh around 105 (which is average for my age) but i wanna lose some weight in my thighs, legs, and butt. Anyway... for like the past 2 months when i come home from school I start eating like a bunch of junk food like alot of chocolate (iv been craving it alot) and cookies, and more. And even when im full I keep eating because it taste so good. And I have told my mom to please stop buying junk food but she just keeps buying it. And there arent really any activities i can do after school to get my mind off of the food. Please Help! i dont wanna gain anymore weight... I want to lose it