WEIGHT QUESTION, please help!!!!!?

so i was a cheerleader and after the season ended i had no other sports. before cheer i was a gymnast so i had a lot of muscle. like A LOT of muscle. i lost some of it doing cheer bcus there wasnt as much conditioning. but anyways. cheer ended in the beggining of march and since then i havent done anything except sit around eat junk food and watch tv and listen to music. id say that 90% of my muscle is gone and since march i have gained 15 pounds. of fat. most people say they cant tell and i guess its not that obvious, except i got some cellulite and stretch marks and my stomach and thighs are bigger but so are my butt and boobs. im around 4' 11" or 5' and 14 years old. during cheer season i weighed between 80 and 85 pounds. now i weigh around 100. i havent really tried dieting or anything but i really want smaller thighs and a toned skinnu stomach. and to lose the fat, but in a healthy way! anything helps! please answer