My boss is having an affair with my ex g/f (I think)?

I don' think that you still have feelings for that woman. I think that you are more upset than anything else that she can get involved with someone else that works at the same place. It probably tares you apart that she could get involved with a man from the office that is also your boss. But she is your ex now and it does not matter if she's involved with your boss or not. If this is the case then this can be an office pattern that she has. She was with you then she is with her boss and then who will be next one man that she gets involved with that works in the same office. Don't lose sleep over this woman because she is not worth it. As far as your boss is it possible that he giving you a hard time because he knows that you were once involved with your ex which is now his girlfriend and he feels threatened by you. Could that be the case?