I have done the unthinkable! We were drunk and I slept with my girlfriends fiance. OMG and WTF am I going to do? What kills me is that he will be having sex with other women and he is engaged to my soon to be x girlfriend. Do I warn her knowing that our friendship will be over or do I let her find out what a dog he is on her own?
Yikes! And I would like you to ask yourself this one simple question. Which feels better, to tell her or to not tell her? It matters not what the reasons are for making your choice. Your work is to get as comfortable as you can with either telling or not telling and then create alignment around your choice, pull the trigger and move along. No drama, no self loathing, no anything other than that. Because at the end of the day this is really more about you than it is about your girlfriend and her fiance. They will go on and do whatever they are going to do and you must find a way to make this right for yourself, with yourself.