I thought it was all just in stories that this kind of thing happened

So I found out my girlfriend of 3 years was cheating on me with her coworker, married man in his 40's, she was 22. I thought it was all just in stories that this kind of thing happened but turns out I was really naive.

She picked up golfing as a new hobby and really enjoyed it, he and other coworkers (woman and men) got her into it. So I didn't think much when she'd go out for a round on a Sunday. One day i asked to go too and pretty much got ignored the whole time I was there. So it turned me off going again. One day I just decided out of the blue to check her phone nothing really prompted me just a gut decision found a totally different social media account that I'd never seen before for snapchat, and found messages and literally hundreds of photos and videos she'd sent between them. Also found film of her doing stuff with him on the golf coarse and messages that proved sometimes she wasn't even at golf.

We broke up, she was upset, turns out he cut her off too, to protect his marriage. So she was left with not a lot. Felt bad for a bit, but don't now. I wasn't overly mad just hurt.