GYOW

I know this sounds really bad but just hear me out. it's been eating me up inside so I'd like some feedback.

We're currently college seniors and we started dating only 4 months ago. For his first two years he was dating another girl that I somewhat knew since we're in the same sorority but I wasn't close to. I had a crush on him since basically freshman year but I knew he was dating this girl.

Anyways they ultimately broke up because he suspected she was cheating due to rumors about a party where she reportedly danced and kissed some guy. I was also there but I don't remember seeing her since it was a huge venue that was hosted by our sorority and we didn't really have overlapping friends circles.

So when we started dating he was obviously still really torn up about his ex and questioning their break-up. It really stung to see him still so torn up about it, since all I wanted for us was a new start and for him to forget his ex completely. So when he asked me if I had seen his ex at that party, I don't know why but I lied and said that I had seen her with other guys. That really sealed it for him and I think he's moved on a lot faster. He says it's a no-brainer that they broke up because she cheated and now he knows for sure. He says he feels a lot better knowing that he didn't dump her for no reason.

I know there's nothing to gain by telling the truth now. He's so much happier than before and he has no regrets about his exgf anymore. So, am I the asshole for lying and keeping up with the lie?