How can a 14 year old girl lose weight?

I am 14 years old, only 5 feet 3 inches and I weight around 148lb! I really want to lose weight! And it doesn't help since all my friends vary from sizes 00-3!!! I don't eat much junk food, or soda! We don't even have much junk food in our home! The only junk food we have is soda,hot cheetos&doritos, and ice cream. I only drink soda on weekends, and I don't like hot cheetos or doritos. And I exercise. I've been going to the gym atleast 3 days a week because we were really busy, but now that it's summer I'll be going a lot more. How can I lose weight? Please don't suggest pills because I want to lose weight the right way. thank you so much!