So, last night I am out of town until quite late and knew that my girlfriend would be going to a bar with some of her friends. We got home at similar times and, as I normally do, I greeted her by sliding my hand over her butt. I noticed pretty quickly that she was not wearing underwear beneath her skirt. When I quizzed her on why she said that it was "to prevent bad lines from appearing on the skirt". Surely I would have to be a total idiot to believe her right? The classic reason for girls to not wear underwear to bars is to either "get in the mood" and arouse themselves for flirting or to straight-up make it easier for cheap, casual sex. She said this was a stupid thing to think and that people would just push their underwear to the side or down if they wanted to do that.

This morning I realised that it's awful even if she was doing it to stop lines appearing on her skirt. I mean, why is it so important that her pussy and butt areas look great for all the drunk dudes at the bar? The more I think about it the more worked up I get. What do you guys think?

Edit 1: Thanks everyone for your comments. The main thing I'm getting is that yes, I already know what I need to do and that it also doesn't really matter if she actually fucked anyone else. This whole issue has actually made me step back from her, in an emotional sense, quite naturally. I think that's a good sign. I am not worried to lose a woman who acts like this even if she is still "faithful". Here's what I am going to do:

  1. I am going to hit the gym HARD. Today.

  2. I am going to go out this weekend with my mates. I will not inform her of my plans and I will have no regard for what I do and how long it takes to do it.

  3. I will continue to fuck her but the emotional, and financial, investment ends now. As a side note, I am quietly hoping to parlay this into getting her to do some of the things she won't do for me sexually at the moment - anal, cumming onto her face, FFM threesome etc.

  4. I'm a valuable man, and it is a seller's market. She has posted a poor bid and now must wait for others to have their turn.