Help with losing weight?

I rarely eat, and when I do, it's something healthy. I exercise the average amount, and use an inside treadmill (because it's too hot to go outside in Phoenix). I'm 5"5, almost 5"6, and weight 120 lbs. I really want to get to somewhere between 95-105 lbs. I'm around 14 years old, so I can't order any dieting programs, I just got a job as an assistant watercolor teacher, and don't have much time to go to places like Jenny Craig. What can I do to lose weight and get to my ideal goal?