I (22F) had sex with my BIL (39M).

Wow, so I feel like I‘m playing a part in the worst soap opera right now. Also English isn’t my native language, excuse the errors!

My boyfriend and I met a Christmas party in my home town last year when I was visiting family. We didn’t know each other personally before, I just heard about him because we work in a similiar field. We immediately hit it off, however I live about 200 miles away and was just visiting. We still made it work with long distance and although Rona hit, we‘re still Skyping almost every day.

A week ago it was his birthday, obviously I couldn‘t be there. He told me he was celebrating with his sister and her boyfriend. We had a Skype convo earlier in the day, some brunch „together“ and then I let them be.

Then he sent me some pictures of their „party“ and my heart sank. I recognised his sister’s bf - it was a guy I had a „ONS“ with once. I won’t go into too much detail but I was way too drunk and just not physically able to say No to things that happened. I don’t think about it every day anymore but there used to be some dark times.

Now, I asked my boyfriend sort of jokingly (because I didn‘t know how to phrase it) who‘s that guy and he told me about the relationship. And that’s when I also found out that when it happened, his sister and the boyfriend were already in a relationship. I‘m not able to remember everything from that night but I‘m a 100% sure he told me he was single before we went to his place.

I just don’t know what to do. I feel like I can‘t tell my boyfriend or he‘ll break up with me and I don don’t want to lose him. I love him. However, the thought of this guy being potentially my in-law makes me puke. My anxiety is through the roof. What the hell do I do?

Tl;dr: Found out our „in-law“ is a guy that potentially cheated on his gf with me and abused me whilst at it. Never told anyone. Wth.