I think I have manic depression. I don't know what to do?

Ask for help. Ask for help from your doctor or see a psychiatrist will be a good start.
See a psychiatrist. The sooner you get treatment the better. There is very good evidence that the more episodes you have, the more frequent the episodes become and the more severe the episodes become.
It's important. not guess. Our mental health is a serious matter and warrants thorough evaluation. Once evaluated by a psychiatrist or clinic psychologist - if you do have a mental disorder - a treatment plan can be developed. Take care.
Mood swings. Manic depression, now known as bipolar disorder, is characterized by swings of mood, often extreme, and these swings can happen slowly or quickly, even several times during a day, especially if left unmedicated. Manic phases can even become psychotic. Get a full psychiatric evaluation, describing what bothers you and consider medication. Also ask for a referral to a reputable psychotherapist.