I've known this guy for around 7 months and we have friends in common. Recently we hooked up a few times and I enjoyed it and was going to maybe broach the subject of us maybe making it a little bit more permanent but that's not going to happen now because I've also just found out he has a girlfriend. Who he's been with for 3 years!!! I only found out because a mutual friend saw us innocently talking and mentioned it because she's really good friends with the girlfriend. Up until then none of the other people we hang out with had any idea because there's nothing on his social media that suggests he does and he's never mentioned having one.

So my question is, if you slept with someone and then found out they had a partner would you feel like you were in the wrong still or would it be down solely to them because they're the one with the partner and therefore in the wrong?