This is almost scary how similar your situation is to mine. My girlfriend told me almost the exact same thing about 3-4 weeks ago. My thread is here
http://www.tfproject.org/tfp/showthread.php?t=95898 in case you want to peruse it and see what advice people gave me and maybe apply it to your situation.
I completely understand your pain and your indecision about whether or not to keep in contact or cut it off as I've been debating the very same thing ever since this happened to me. I know that it is in my overall best interests to limit contact as much as possible but I'm just not able to do that right now. I'm not emotionally strong enough to handle that rift between us, at least not yet.
Unfortunately I can't really give you much advice at the moment as I'm still struggling with the situation myself, but hey, if you want to talk about it PM me and we can help each other out. The best thing I can tell you is to keep busy, try and go places where other girls are, and socialize. I know that doing that is harder than you want it to be as I'm in that position right now, but hanging out with friends and playing video games or going to parties really does help ease the pain.