You might want to visit your family doctor in order to evaluate if your condition needs medical treatment. He might refer you to a psychiatrist for further examination and to determine the most useful treatment if needed.
It is not uncommon for teenagers during puberty to feel depressed. It is a period of big turbulences in one’s life: bigger problems, trying to make more achievements in order to get accepted from the others. This condition might be frustrating. You might want to talk to your friends or to a counselor before you seek for medical treatment.
It would not be wise to try to treat the depression by yourself, especially not with medications.