You've posted this before and if I remember right many people told you to talk to him.

And it's almost too late now to talk to him. I would talk to him soon just because of the slight chance he chose the other girl because you showed no interest.

In a perfect, fairy tale world he would tell you that it is you he wants and breaks his engagement.

But more than likely he just has a cheating heart and would only use you but still stay engaged.

You'll only know for sure by talking to him and telling him how you felt/feel. If after that he tells you he has "broken" it off with her get confirmation from other friends before acting on it. And, likewise, if he says he wants to be with the other girl then walk away totally. If still hard for you at work then maybe a new job or transfer? If you didn't have to see him at work you might have been well along on your healing/recovery from it. As it is you have co-workers stirring things up.

He has the answer and you'll only know the answer by talking to him & being honest. Just be careful you don't become a player in a "cheater's game". You wouldn't want it done to you so don't do it to someone else.