How do you get over jealousy?

I have really taken a liking to a friend of mine but she doesn't feel the same way and it tears me apart inside. I always feel paranoid and jealous when I hear her voice as she lives across the hall from me and sometimes it gets so bad that I cannot get to sleep until the early hours of the morning. On top of this I am about to declare myself bankrupt and lose my career. I have also lost my trust and confidence in my friends. There is other stuff going in my life at the moment as well that is causing problems. The last 12 years have been pretty bad. So I am feeling lonely and frequently consider suicide as a way out of this miserable and tiresome existence. I have tried to make an effort to change but I'm also very shy and lack self confidence when it comes to meeting new people which is an obstacle I can't overcome. Psychotherapy didn't seem to help, perscribed drugs didn't help.