Murphy's law: whatever can go wrong will go wrong and at the most inopportune time. Try to interact here and online with friends and family. Isolation is not good for grieving hearts: I found that out the hard way. I don't know your ex-gf but she doesn't sound like the type of woman that is worth shedding tears over. Your emotions are better spent on someone who's decent, loving and respectful.
It's quite natural to grieve in your situation: you're human, you feel and therefore you suffer. It's the name of the game.
Take care.