Unable to move forward

We were friends/colleagues for over two years and then we dated a little last year. He was going through some deep depression and as we just started I was unaware and didn't know that he was in dire need of help. He disappeared on me after a few weeks of dating. I really liked him and was deeply affected by his disappearance. I found out a few months later that he started dating again. The dumb part was I still saw him at industry events and one day we were left alone. I yelled at him for his horrible behavior and cried. Then I said please leave me alone as I truly cared about him and am heartbroken. He went into a sob story about how he was depressed and attempted suicide. He started to be my friend again and the chemistry was undeniable. He kept telling me that he wasn't in a serious relationship and he started to flirt with me and we started seeing each other again. I was keeping him at arm's distance and was being a little more careful the second time around. One day I asked him if he was still seeing other girls and after a long discussion I find out he is seeing a friend of mine that was in the same industry organization as us and that they already met each other's family and friends. My heart was shattered. She knew I dated him and that I was crushed when he disappeared. So it was like a stab in the heart. After the initial shock, I sank into depression. It has been months and I still run into them at industry functions. I have held up a strong front for months and I am getting emotionally drained. I can't explain why this has affected me so much as I am normally a really strong person. Should I quit the organization and stop attending these functions until I am emotionally healthier? I just really need advice on how to carry on seeing two people constantly after they had betrayed me.

"He ***is*** seeing a friend of mine". "He kept telling me that he wasn't in a serious relationship" He was two-timing- not just you. The pair of you! Depression, my arse. What a great violin act! You've just found out that from 10 feet he's alright but at close quarters he's a two-timing sleazeball.... who apparently has met his perfect woman... whom apparently is such a doormat she doesn't MIND the fact he was two-timing her as well! ...Unlike you. GOOD ON YA! Leave the low-standarded idiots (and what will be their low-calibre relationship) to it. You're destined for a far better relationship with a far better person; one who would NEVER cheat on you, let alone feel like it. *Those two* betrayed you but only because Fate was engineering a huge favour for you with the aid of those two mere Pawns! It's just a matter of time before you get given the second half of it (and feel safe to accept it based on the lessons you've since learned, called, How to tell a good'un). And then - she who laughs last laughs longest (forever Amen, actually)... with a Knight or a King. :-) I can't wait until he cheats on her again (thanks to her having 'told' him it's acceptable) or she cheats on him, can you? :-) And she will. Because that man was never the prize as far as she was concerned. Well, maybe a tad. But her greatest motivation was jealousy and competitiveness - trying to prove to herself that she was better, fitter, all-round more alluring than you. Yes, indeed, she was. In a way. Because, obviously, snakes *do* find other snakes more attractive than Queens, don't they. :-) No, don't you quit your job. Not unless secretly you want to and are just needing an excuse. Just - next time you see them, tell them how they are utterly PERFECT for one other (and that you're qualified to know). I'm sure the smug meaning will 'slide' out via your tone just fine. ;-)