u/Impossible-Radio-230

I am not a native english speaker, so I apologize for any mistakes I'll make. This is also a throwaway, since I don't want this to be connected to my main account.

I know this sounds exactly like those stories, that I scream "Please stand up for yourself, holy crap" at, but please hear me out on this. We've been together for 3 years now and are (were?) planning to get married next year. On Wednesday evening, while I was finishing up some work stuff, my fiancee came up and said he wanted to talk to me. I assumed it was nothing too serious, since, except for some smaller fights, we've never really had a "rougher patch" and I'd call us a pretty healthy couple. But, as you might know from the title, I was wrong. He confessed. He said he cheated, only once and while he was drunk. He had met that person at a bar, and then he had never seen him again. My head was just spinning the whole time I was listening. I was just dumbfounded. After he finished we both just sat there in silence. I could see him glancing at me from time to time, but I just kept staring at the floor. After what felt like ages, he asked me "Do you want me to leave?. I declined and told him that I'd leave and I went for a run, since that's usually how I resolve my problems. I came back around 1am. I'm currently working from home, so I didn't worry that much about the hour. (My work's parking lot is completely torn down right now, due to some kind of sewage leak.) We both have a location sharing app and I got notifications that he checked mine multiple times. I always like it when he does that, since I find it kinda cute that he worries about me, and despite everything that happened, it still made me smile. He was still up. I had thought about it and decided that I was willing to go to counselling. Not only did he come to me with this, but I also love him so much and couldn't let myself just give up like that. Before I even had the chance to say something more, he just declined ??? He said that he just "couldn't do that to me"? What?

Here comes the part, which you have to hear me out on. I talked to my friend (27F) about this. She said, as all of you probably think too, that he lied about the quantity of his cheating/that it was more serious. I genuinely don't think so. I really cannot believe that he would do something like that. He is the best person I've ever met. He had helped me through so many of my tough times and I know how much he'd looked down on cheating. I cannot get myself to believe that that man would cheat once, let alone multiple times. She looked at me like "are you serious rn?", but I genuinely think that. I just have this gut feeling that something isn't right.

Then why would he even do that? No idea. The only other explanation I can come up with is that something else happened/he thinks that maybe I cheated and wanted me to confess? (If that were the truth I'd be even more surprised) I think I just need to talk to him, but I have no idea how to approach this. This is not the same person I've known as my best friend for the past 6 years and my partner for the last 3. Is this just me being pathetic? Probably. I just cannot let go of this. I just need some other opinions on this. This just makes my chest hurt so much and I just feel so disorientated. He's currently staying with his parents, since I don't even have anyone to stay with here. I'll be able to talk to him this evening, when he finally gets of off work. It's just this gut feeling that I get when I think about it. I just keep thinking that I know him, but then also feel that I'm too dazed to think straight. I'm currently laying in bed and writing this on my lunch break, so what should I even do? Should I just tell him this straight up, despite how ridiculous it it? Should I just accept that I'm going crazy?