Dude, I can imagine how you're feeling. My ex broke up with me about a month ago, she was my first serious girlfriend, we had been going out for just over a year, and then one day, on MSN of all places, she tells me that she doesn't love me anymore, and that I'm not giving her space. Hearing that totally broke my heart, it hurt so much because I never ever saw it coming.
In all honesty, I knew the relationship had begun to change, because it was a long distance relationship, the last time I saw her she treated me as if we were best friend, whereas three months previously we had been passionate lovers enjoying every moment together. What f**ked with my mind even more was, a few days after the spilt when I was feeling utterly miserbable and heartbroken, she rings me and told me she regretted what she had done and that she still loved me. Man, my mind had never felt so screwed in my life, but I told her that we couldn't get back together as things would never be the same.
I have gradually tried to phase her out of my life, as in other cases mentioned, it just brought all the emotions I had felt bubbling back up to the surface. What was worse, she moved on so quickly I had begun to question whether or not the relationship had actually meant anything to her. I phoned her one day, and she was telling me about her new bf, not only that she was telling me about their sexual activities together too. This made me feel so jealous and angry, I have never felt anything like it. Things seem to be getting better though, we are friends and we can talk and things aren't so bad.
But, as everyone else has said, time is a healer and there is no telling how long it can take. But be assured, you're not the only one who has felt such sharp emotional pain, and many people know what it's like and empathise with you, I sure do.