First off, been there. Is this your first serious love ? Hurts like hell. But, have you learned anything from this ? Life sucks, yeah, but you dust yourself off and start all over with what you have learned. And everything happens for a reason.
Can you start getting involved in other activities, including physical exertion and workouts, and I agree with what mercurygirl has said. She gave a good woman's perspective on it. But, if you contact her--would you get a straight-up answer ? Would an answer from her make you feel any differently ? If she blamed you ? Or if she blamed herself, there would still be a nagging feeling that there still was something that you "didn't do right" that would have kept the relationship going? Be prepared. I would also add....maybe she is concerned about your sexual orientation and that is fair. But that could be discussed...
Or, can you just try writing down on paper all that the relationship meant to you and how much it hurts---but don't send it? Just take it outside to the nearest beach, or forest or field, tear it up and cast to the wind. It'll mean closure to you and you will remember the good times you had with no regret. And can go on to fall in love again.
Here's my experience with my first head-over-heels love. a: I moved way too fast towards settling down b: I was infatuated c: she liked to date many men and married ones, to boot, and d: she lied about having a serious illness in order to either get out of the relationship (most probably) or get more attention for some reason. Would I have forgiven her for what she had done at the time ? Damn straight, she was a knockout, funny and gave the best oral that I have ever experienced since. But she would have been a horrible mate.
So, get back 'out there,' ask out some women, let them know upfront that you just broke up with someone but would like to just hang out and get to know them, that it may possibly just end up a friendship, would that be ok. Get some weight back on you, get a good tan, buy some new clothes; looking great is the best revenge.
Best of luck in this, keep in mind that this happens to humans and it takes time to get over all the pain. If we didn't feel it though, we would be dead souls, so be thankful to your Creator that you have this inside of you.
PS. I think she's very immature to have dealt with this in this manner; is this the type of person you would want to have a relationship with, who handles life's major problems by avoidance ? Not a great quality to have. She may also have some type of an ego thing, you were something to pursue and once she got that, she was done. Both sexes can have that trait. In my opinion, she may attempt to come back to you after some time passes and she realizes that you were a pretty good catch. Watch out for your adoration as it may get the best of you. Run, do not walk. My opinion.
Finally, obsessing is not good for you--if this continues, after 4 months, you may think of going to a counselor, it's up to you.