Ok... So long story short, I split with EA DP last August after discovering his affair and we have one DD together.
I finally got it all together and was enjoying life, until I got 'chatting' to a hot single guy who happens to live next door... 
We took our time and began seeing each other, him being keen and really putting effort into dating and getting to know me.
Speed forward to 3 weeks ago when we were on a weekend away in London (all paid for by him and his idea) and I have a Facebook message from his Ex asking if I was seeing him. I told him about it, and we both agreed to ignore it and to block her as he said she'd been trying to cause trouble for him before with a previous relationship.
The week after she messages me again, this time from her daughter's account, saying he's been seeing her, and then she sends me screen shots of texts sent from his phone to her and they were bloody awful and backed up everything she said...
Obviously I told him were to go, and he said he was dissapointed that I never gave him the chance to explain blah blah...So I did and his reply was I don't need to explain because I haven't done anything, there's no going back for us, this is all spoilt things between us. We are obviously not together now, he is still protesting his innocence, but he doesn't want to get back together. This only happened 2 weeks ago, so it is still quite fresh and raw in my mind. The kick in the teeth is that this has all been done via TEXT and the asshole couldn't even pick up the phone to talk to me or walk the 15 feet to my house to knock on the door.
I am still hurting over it, I don't want him back, but I feel like I'm greaving for what I thought we had and I have to deal with the fucker living next door!!! 
I'm happy enough by myself, have a great circle of family and friends, and have the next 3 weekends filled with things to do. The questions I am asking is 1. How the hell does someone who put so much effort into you do that, and 2. When will this horrible feeling go away?