I can't stop eating o_o.. doubleyew tee eff (WTF)?

Mmmkay. So i'm a 13 year old guy and I can't stop eating o_o. Like, I will eat a sandwich, a hotdog, an icecream sundae, then get a cookie or something... FOR LUNCH! Crazy right? But anyway, I used to be like 140 lbs when I was 5'2, i was 12 years old, but i lost alot of weight and got down to 110 without even going on a diet, but since ive been eating like this for the last few weeks, im already up to 120, its horrible. Sooo yeah, what do I do?