Last year (15yrs together) he up and left, telling me he found a roommate (we had communications about seperating in the previous few weeks before he left). I discovered this "roommate" was actually his girlfriend. I found out via Facebook, she had put up a pic on his wall calling him "the best boyfriend ever". So humiliating. Two months later he was begging me for a second chance and stupidly I gave it to him.

when they try to make things look all innocent, meanwhile ... .
My ex still claims that his affair was my fault. I wasn't "loving and spontaneous" enough. How I was supposed to be spontaneous without help was beyond me and opened my eyes that I'd never be good enough in his eyes.
WOW RefuseToSeccumb! Not spontaneous and loving enough? This is
exactly what my BPbf accused his ex of (his one and only relationship before me). Exactly. Not loving and spontaneous enough. He made her feel real bad about it too. He told her she needed to be more like his (now) ex-housemate! What an insult to any decent women to be told to be like that trashy woman.
Here's what I have come to realize about him. No matter how much I do for him, he can't appreciate me, because he is not living in the present. He is stuck in the past, idealizing his ex even though he didn't appreciate her when he had her and made her feel awful. 4 years on he still can't accept that she has moved on and is married.
On the other side, he is living in the future. This involves his fantasies about his slutty ex-housemate. He knows in his heart that he couldn't put up with her if he got her to settle down with him, but still he lives in lalaland.
Then there is me stuck in no man's land while his head is in the past and the future. I have come to believe that he, and probably all BP, can't appreciate you while they've got you. It's only when you are gone and they eventually get to that place where they realize what they threw away, that they suddenly want you more than anything. Can we ever "win"? Is it even worth it for me to share my theory with my BPbf?