For privacy we'll call him J. He and I had been friends for years so when our relationship turned physical I didn't think twice about it. I trusted him with my life and seemed to be able to forgive and find reason for all of his mistakes (he made many) not even a month into our relationship the idea of sex came up and we both were okay with it. I was a little hesitant because I hadn't gone very far with boys before but he had already lost his virginity so I trusted that he knew what he was doing. we were safe about it of course and knew all the risks. we made an educated decision. One night he came over and we got down to it, it wasn't painful or anything so the actual act didn't bother me; what bothers me is what happened a week or so later. Unbeknownst to me he went and hooked up with one of my bestfriends (we'll call her L) a girl he'd already cheated on a prior relationship with. My best friend (lets call her E) franticly messaged me a screenshot of her boyfriend saying that J and L were hooking up and unfortunately I could believe my eyes. I confronted him about it and was met with a load of lies saying another one of his mates was just trying to prank me and had gotten on E's boyfriend's phone. I believed it but continued to be suspicious of the whole situation. A couple days later an unexpected person decided to come forward and tell me the truth, that what I'd feared was true. Armed with more screenshots I confronted him yet another time just to be lied to; But this time I pushed and pushed until he finally admitted to "maybe kissing her once" but he was apparently so high at the time that he couldn't stop himself which I don't believe for one moment. "possibly kissing her once" quickly turned to people confessing that they'd heard J and L talk about having sex with each other. Though everything I've been more disappointed in the people that were my so-called "friends" because all of them know for a fact that I would have come straight to them if they were in my position instead of helping harbour  secrets for a stoner fuckboi that treats all of them pretty badly anyway.