dont worry if you cant lose weight on your own a doctor can help, they even give you recipes to follow, and tell you the reason you cant lose weight.
There can be a medical reasons why you are not losing weight such as hypothyroidism so it would be a good idea to see your doctor/pediatrician. Also, do not make the mistake of skipping meals hoping that the lack of calories will help you; it actually works the opposite. When a person skips meals, the brain gets tricked into thinking that the body is in starvation mode and therefore the brain tells the body to hold onto every fat cell!! A lot of people don't know that, especially teens. Make sure you eat three good meals every day and continue to exercise. Also, you should never lose more than 2 pounds of weight per week. another thing you need to know is that weight loss often times plateaus so you may be going along losing that 1 to 2 pounds per week and then all of a sudden, drat! you stop losing weight for a couple of weeks. Don't give up, hang in there and the weight will start to drop again. Another thing is the type of exercise can make a difference. If you are doing muscle building exercises, the weight of the muscle will cause you to think you aren't losing weight; you actually have, you've just replaced it and your body is actually better off. hang in there!