My (25F) boyfriend (25M) of 5+ years asked me for a threesome with one of my close friends. We were all at a party and pretty messed up at the time and he suggested it to me. I was shocked because we had discussed that a threesome was not something we would ever want to before as a couple. He claims that he was just not thinking rationally, didn’t think it through, and he doesn’t actually want a threesome when thinking about it sober. I feel really bad about myself and inadequate now (seeing as he basically asked to sleep with my friend), and also have lost trust and confidence in our relationship. We’ve always talked about how we have a good sex life but now I’m doubting he is telling the truth about that. We have been talking about marriage and children and he himself has always been quite jealous of me and we have had lots of conversations about being monogamous so I feel like I don’t know him now. How am I supposed to move on from this? Could this be a reason to break up? I’m finding it hard to see a way forward.