Go out and fuck 10 other women, and I bet you wont be thinking about her anymore
But seriously, If you try to interact with more people, and most importantly GET OUT OF THE HOUSE MORE!, you will probably find that you start to get over it and probably dont even give a shit about her anymore(relatively speaking).
Staying in your basement ruminating like you have been for the last 3 months is probably the most unhealthy thing you could have been doing. If you absolutely MUST ruminate, Its best done outside the house, and its also good to talk to other people about it. Other people are more likely to notice when you are being illogical and looking too deeply into something petty.
But basically find something, anything, that you can motivate yourself to do, and let it occupy your mind once in a while. You'd be surprised how much even a few hours of relief from thinking about the problem can help.