Fuck, man. That's well shit. As the guy that walked away from ex with no real explanation and an awkward kiss on the cheek, less than a month ago, I won't lie - it's going to be sickening, for the first few weeks or so. You start to realise that maybe she did have another motive, and that makes you feel better/worse, because she's the cunt (that was my thoughts - not saying the same thing happened to you). This situation sounds a lot like mine, so I do get it.
There was no chance I could be friends with my ex - we always said that would be the case, if we ever broke up. It would be too hard to try and get back to that level.
See some friends, RLP. Don't lock yourself away, because it fucking eats at you. Mates will steer you away from that, and get you back into the socialising mindset (one thing I lost out on, because I generally was told what to do - for the first time ever, to be fair). This whole post is a bit of a mess, but it's just me trying to get everything I'm thinking out. Whatever she thinks, you obviously deserve to happy. Go and make yourself happy. All the best, mate.

Don't think of doing anything stupid, seriously.