Girl I have been there...it sooo hurts! Had he promised they were "over" prior to this? Or was it just now you confirmed the "more than friends" idea?
OUCH!
Yeah, take some time for you. Relax. Something tells me he wants to tell you his side of this story. When he does (and you do want to hear it, don't you?)...try to get it in person. If it's something like what happened with CJ and his OW toward the end...it was something he wanted out of but she was holding some threats over his head. You can read a story like that but the best way to trust it's veracity is to watch the person tell it.
CJ was remorseful, he looked me right in the eye and said he knew he'd blown it with me forever. He was crying. (Not typically a cryer). He told me what had happened over the past 3 months and I had a choice...believe him, or not. I just believed him, it seemed right in a way his other "little and not so little LIES" had not.
What is my point here....when you are strong enough, centered enought, vented here enough ...why not try to give him an actual chance to explain? Would that be a 180? I know it was for me in my circumstances!