Wishing I wasn't so upset...?

So it has been a few weeks (2 or 3 maybe) since the guy I was seeing and I called it quits. And I just found out that "I'm so confused" and "It's not you, it's me" really means "I have been having late night talks with my ex-girlfriend from over 10 years ago who has been married for 10 years and has 6 kids because she is fighting with her husband and I want her to realize she should be with me". Basically, all of a sudden things just ended. And I thought I had done something wrong or that I was putting pressure on him.....and the truth is, he was just getting reinvolved with this girl so to speak. I am so angry. He doesn't know that I know....not that he would care. But I'm just.....so angry that this guy, who apparently has feelings for this girl and is confused, sat there and got involved in a relationship with me. He sat there and told me all these things-which is what liars do, I know. He even went so far as to call his mom and tell her I was the one. I'm so great, I'm the one, he sees a future with us.....and all along she was calling him at night to talk about her problems with her man and he sees a window there. I really feel like an ***. And I know I shouldn't because.....well, I didn't really do anything, but I'm angry and I don't know how to deal with it. I really just needed to vent. Thanks