Hi jb, sorry you are here in this crappy situation but at least we are all in the same stupid boat together and can help one another.
Your story interests me as mine is extremely similar. My H had an OW at the office but it didn't really work out as the OW didn't want a relationship with him. They continue to have sex as friends with benefits as far as I know. But he has also started dating and having sex with other women. I feel that it is part of his experimentation to find himself, somewhat like your W is doing. We also have no kids, no house, no logistical reason to stick together.
The only reason I have for staying around is that we had a wonderful relationship for the most part before he went into this stupid behavior. But now he is being a selfish jerk and I wouldn't want him back as he is now. So what to do? Only you can decide what your next course of action is.
I think most vets on here would tell you to wait. There is not really a reason to file for D now, is there? I mean, yeah you want to show her you won't put up with this crappy behavior. You want to punish her. I get that. If there are financial or legal reasons why you need to start the process now I get that, but it doesn't sound like it.
My best advice to give you is the advice I got from great folks on here. Focus on yourself and do not pursue her for now. If she initiates contact, great. Do what you like, respond or not. But don't contact her for now. Act like you are just going to move on with your life, and do so! Go get a life and enjoy yourself. Act like you are fine with her moving out and doing whatever she does. Act like you are divorced already, why not. If you really want to file for D then just act like you did and wait and see if you want to after some time passes.
They say if you let her go and stop trying to control her the chances are better that she will realize the mistake she made. So the quicker you can let her out of the cage so to speak, the sooner she can realize the grass is not greener and single life is not a bowl of cherries all the time. They call it a fog that they are in and until that fog lifts your W will not see or do things in a logical way.
I hope this helps you a bit. Maybe check out my threads for some of the advice people have given me. Good luck!
Me: 34 H: 30 M: 4 years BD: 6/15/14 He moved out 6/30/14 OW1: EA then PA after BD Now he's dating multiple OWs I'm over it and moving on.