I just want to offer sympathy and a hug. My last breakup of a serious relationship, while not at all sudden, was messy and ugly and just fucking weird. It took me a good six months to get over him, after a 2 1/2 year relationship. Once I grieved though, I was able to jump back on OKC, kiss those darn frogs, and finally find some guys for fun, some that didn't work out for various reasons, and finally one that, so far (2 months in) going really well.
I feel more cautious with my heart now, due to my ex and what he put me through. It was a blow, and made me rather bitter for a while, and there's a scar in the trust part of my heart now that I think will always be there.
Take really good care of yourself, do good healthy things, cry, laugh, distract yourself with your other partners and friends. It's OK to curl up in a fetal ball in bed sometimes too. (Not all the time, but sometimes we just need rest.) I know how much this kind of thing can throw you.
BTW, the Facebook thing? I didn't unfriend my ex for a couple months. I was also FB friends with the married couple he was seeing towards the end of our relationship. Finally I unfriended the 2 of them, then my ex. I did have an unhealthy habit of checking up on them, and it felt clean and good when I finally closed that chapter.
My primary partner is still FB friends with my ex though, and once in a while they chat briefly. Which is weird, especially because if I am tagged in one of her pix, he can see it. Oh well.