First off, I am sorry you are going through this. I also had an ex-fiancé who was having an affair with their married coworker, I went through those same emotions. It was to the point where I looked up as much as I could about the AP just to expose both of them. I never went through w/it but I would be lying if I told you that I don't still fantasize about it. Truth is it won't bring me or you any piece. It will most likely not have the desired outcome, lastly you are showing that you are still hurt months later. Best thing you can do is focus on yourself, and stop letting them live rent free in your mind. Easier said than done, but you will get there with time.