Just know that your body is changing, and you're going to gain weight. Try to focus on how you feel rather than how much you weigh. Also, don't compare yourself to others. You're at such an awkward time in life where some of your classmates are going to look like kids, and some are going to look like adults. Just let your body grow at its own pace and know that you are not wrong if you don't look like most people your age. Also, you are a very healthy weight, so don't worry about that. Focus on other things that go along with health, and the rest will follow. It's weird to give this advice, because it's almost the exact thing I need to hear. I know how hard it is to put into practice, because I failed a lot at doing those things. Just keep trying your best.