The way I see this is that the lack of communication is to blame for this whole thing. Sure you have bad points and thing you might need to change, but I'm sure she does as well. My point is that she should have talked to you about this before she decided to break it off, not after. If anyone is to blame then it is her, not you. what you need to do now is talk to her properly face to face. It doesn't matter that she is seeing someone else because 4 YEARS really means something! Sit her down let EVERYTHING come out and let her do the same as it is the only way of finding out true wants and feeling of both parties. Maybe then you can come to an agreement on issues. Whether it means you guys get back together or not, you will at least know where you stand with her and it will stop you going insane. Good luck, man - I hoped this helped a bit.