advice or something ???? please !?

Well, you know that you don't need to lose weight. I think you're more looking to tone (and if you're not, you should be). Exercises like yoga or pilates will really make the difference you're looking for, and your parents should be cool with it because the goal in such exercise routines is not to burn calories, it's to strengthen and elongate the muscles. Be careful, though. Your body is still changing and developing, it won't settle down until you're 19 or 20.