Help me. Pleasse

How do you deal with despair? Constant crushing despair? This girl that I was talking to you, there's a lot of situations through out all of it but we were talking. And then she just stopped. And to add a little bit I've always dealt with depression and despair and just not caring for as long as I can remember. This was the first girl I ever really fell for. When does this pain go away? How can I become someone I'm happy with and that I can just feel happy or at least not feel like I would be better off underground not having to deal with any of this. Please help. Ask me questions if you need clarification.