I dance and walk alot but my diet isn't great?

so im 13 and weigh 200 pounds. now in freshman year i take dance cl 3 times a week and i walk up and down stairs all day and walk one mile two other days to my internship/job thing. but my diet isn't so great.i eat munchies but try to cut back slightly and i drink soda and eat all those fast foods. ive tried to stop but it just doesnt work for me what can i do to try and lose weight more?? idk what else,i dont eat alot tho usually just some yogurt in the morning,what ever they give during school for lunch and then wait to get to home which is when i begin to munch on stuff here and there untill dinner which sometimes will be something big like rice,beans and chicken or little like pizza or cereal