If you really mean that you have a constant erection that will not go away even after repeatedly masturbating, you may have a problem worth seeing a doctor about. However if you mean it goes down but keeps coming back after about an hour, this is probably just your hormones running riot and may be ignored. Seemingly uncontrollable erection is extremely common at your age, but rarely talked about. It can be kept at a tolerable level by quick j/o sessions, until your d*** learns that you are the master or you get older! This will happen, I promise you.