I'm sorry you're going through this bump in the road but you really must get past it. I know you don't enjoy being miserable but you're holding on to this so tightly that it seems to have become an obsession.
You don't say how old you are; regardless, you need to make a firm commitment to yourself that you will move on.
1. Get rid of anything you still have that has any connection to her. No pictures, no letters, nothing. If you have a cell phone, get rid of her telephone number. If you have still have those around you'll never climb out of your rut.
2. Make yourself take up a new interest. You need something to fill the emptiness you feel. Even going to a gym--physical exercise is a good way to get exhausted and fall to sleep (and make yourself feel better). You'll meet people who will have at least one thing in common with you and that's a way to begin friendships with both men and women.
3. Find a way to enjoy one thing each day. It doesn't have to be anything big--a pretty sunrise, a song on the radio, something in a store window, whatever. If you can find a bit of happiness in your sorrow you know you'll feel better.
4. Whenever you feel a thought about her coming on, get it out of your mind and put something else in there. It will be difficult initially but over time she will become a distant memory. Don't let your sadness continue to rule your life.
Hope these few things help.
Good luck and do keep posting.