Well, I’m sorry to say that it sounds like you were dating a guy who enjoys being a “player”… someone who is more interested in the chase and new conquests than relationships.
This, I have no doubt, has been a very painful learning experience. I’m sorry. So, what’s the lesson you may ask? The lesson is to understand that a liar is a lair and a cheat is a cheat. Regardless of what people may say, it is their actions that speak the truth. Based upon your post, this guy has lied to, and cheated on, his previous girlfriends. Thus, it is highly likely that he will lie to and cheat on future girlfriends. In short, the best predictor of future behavior, is past behavior. This guy’s past behavior clearly demonstrates who and what he is — a lair and a cheat.
It doesn’t matter who this guy is with – he will lie and he will cheat.
Frankly, he’s done you a huge favor in breaking up with you. He’s allowing you to find someone who is much, much better… someone who doesn’t lie and who doesn’t cheat — someone who values you and a relationship with you.
As for what to do when you see him in the hallway?
Hold your head up high and treat him just like any other acquaintance — no better — no worse. Do not cry. Do not create a scene. Do not pick a fight. Do not do anything … Act completely indifferent. And, very important, do not (under any circumstances) go out with him again should your indifference spark his interest in you again.
Here are a few columns that might be of interest:
Advice for when you find someone else you’re interested in