<human>: A little background, my girlfriend and I have been dating for a little over a year and are pretty serious about each other. Anyway, before we started dating she told me a story about how her and another friend of hers did "stuff" with a guy on his birthday. She didn't really go into detail but said that the other girl may have had sex with him. I didn't think much of this at the time and had forgotten about it until recently. Sometime in December the story popped back into my mind and I've been unable to shake it. Just the thought of her and another gal with some random guy she didn't know that well really bothers me. I've thought about it everyday for the past month now and it's affecting my workouts and makes me doubt our relationship. I don't think she did anything wrong since we weren't together at the time so I don't really know why I'm so upset about it. 

I really just want to stop thinking about it and move on in our relationship. So how do I move past this? What have you done in the past to help you forget uncomfortable thoughts? Thanks!

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<bot>: Girlfriend messed around with a guy before we started dating, a year later I can't stop thinking about it. How do I move on?