How to make my state of mind less depressing?

I'm starting to wonder if there is something wrong with me. I'm constantly feeling stressed out because of homework and my social life and my future. Most teenagers do that but

-Most teenagers don't become heart broken and break into a symphony of tears when they get a C on a test.

-Most teens don't cry for hours because somebody called them rude

-Most people in general can get over something by listening to music or spending time doing a hobby, but whenever something happens to me I can't sleep or whatever happened will haunt my dreams.

-I stay depressed over stuff for at least a month.

I don't think it's just a phase because I've been like this for years.

My state of mind is just so fragile and pathetic. Am I bipolar? I'm really not sure if something is wrong with me. Is this just a self confidence problem or, do I need help? How do I change this state of mind?