There is enormous variation in the shape and size of an individual's body. Seeing the bodies of models one feels that there is something wrong with our bodies and gives many an inferiority complex.
Based on your description I cannot give you an opinion whether you have an imbalance in your hormones. Please remember that the breasts of many teens tend to become big and then become smaller. This is called physiologic gynecomastia. The hair on your chest is probably normal. I would suggest that you see a physician and once that doctor makes an assessment that there is no hormone imbalance you should stop worrying about your body's appearance.
I did calculate your body mass index (BMI). It is 20.5 suggesting that you are within the normal weight range but at the lower limit. Exercise is always a good thing but the kind you do should be determined by you and not your friends. Whatever exercise gives you pleasure, that is what you should do. If you decide to do body building, please do not have unreal expectations.