UPDATE figured out my fiances disgusting secret

Update: A lot of you are questioning whether or not I SAW the messages between them and yes I did. I would never accuse someone of something so foul without knowing 100% forsure. I saw the entire thread because Snapchat didn’t delete messages back then and I also saw the pictures they were sharing and it was completely inappropriate. It wasn’t a one sided thing. I think he blocked him on his social media’s to stop him from messaging him and getting caught by me since I had access to his accounts. I texted him this morning that we had to talk and he keeps asking about what. Is there a way to tell him I know? Will any good come out of this? Should I just walk away and save both of us the embarrassment? Idk how long it was going on for or if it ever became physical and quite frankly, I would rather not know. I think I’m going to be sick.

Today I was talking to my brother in law and we somehow started talking about my fiancé’s cousins and how they were planning on hanging out after last seeing each other when they were children. We get to talking about his gay male cousin, I questioned why my fiancé didn’t like him since he had him blocked on his social medias 5 years ago when we first started dating and always talked about how much of a weird guy he was. I followed up my question with another question, what’s his name? “His name is Chris” (not his real name) he replied, and it was as if I had gotten told I only had 5 months to live. I couldn’t reply, I couldn’t move. I just stared at my brother in law because I had realized something.

A little back story, when I first started seeing his brother we were not exclusive and I found out he was bisexual through his Snapchat bc he used to talk/sext two different guys. Only these two. One of the guys sc name was a distinctive nickname with the first letter of his name so something like “CBoy👺” I always thought it was just some random dude he had probably met on a website or something. We stopped seeing each other bc he lied to me about his sexuality and he didn’t allow me to have a choice in wether I wanted to date a bisexual man or not. A couple months passed and I realized I really didn’t care if he was into men, just as long as he was faithful once we were exclusive. We didn’t become official until like half a year later but he apologized throughout all that time and gave me any passwords I wanted, to prove to me he really wanted us.

Fast forward to today, he said his name was Chris. I turned pale and it’s like my brain pieced everything together on its own. I immediately found said cousins Instagram and right there on his bio was that same nickname along with his Snapchat name. The. Same. One. He was sexting his own cousin 5 years ago. I am completely fucking disgusted and I couldn’t even kiss him hello today. Wtf do I do?? I can’t look at him the same anymore. How do I even confront him for something that was going on years ago? I am in over my head about this.