Not walked in on but saw a text.
He was my first love, he was also a virgin when we met and we had been together for 4 years at that point (he was 24 at the time). It was a long distance relationship for the most part. I know it sounds stupid but I was way out of his league - I was super self conscious at the time and hated myself. I nevee cared about looks, personality is so much more important. Everybody kept asking me "why him?", he wasn't good looking at all, but as I said there are much more important things in life than looks and besides that I hated "pretty" guys cause every good looking guy i had ever met until then was a complete asshole. (Spoiler: Turns out the "not good looking" guys are assholes too).
His account was logged in (skype) on my old laptop which i barely used. I was about to log out since I didn't care about it and I trusted him at that time - until a few messages appeared containing some really sexual stuff. I opened the chat window and saw that he was sexting with her at that very moment. I was heartbroken.
I kept scrolling up to see how long this has been going on while the disgusting messages kept popping up. Turns out the girl he was texting with was the girl that had just visited him a few days or weeks ago, i believe she stayed with for an entire week. I was always a little suspicious about her but he told me not to worry about it and that they had been friends for forever.
Anyway after crying for several hours (while he kept sexting) i decided to forgive him - after all I loved him deeply and wanted to "fix" our relationship. What a mistake... for about 4 months i kept it a secret. I tried giving him hints, asking about certain things.
I started with normal stuff like "When she visited you, what did you guys do" but then i even went as far as saying stuff like "I know this might sound stupid but is there anything you might want to tell me?" "You know I'd forgive you everything as long as you just tell me about it". They kept sexting almost daily. It destroyed me. I wanted to "fix" everything so bad that I completely ignored my feelings until everything finally escalated. I confronted him about it and told him that I knew he was sexting with her and that I know they had sex (they mentioned it but briefly but they talked about it like it was a long while ago so I wasn't sure if it had happened in said week she spent with him).
However, i told him that I everything i wanted from him in the last 4 months was to confess but he didn't. Even then he lied to me. He kept asking me how i know that they are sexting so i told him his account was logged in - he immediately changed his password. He then continue to tell me that sexting isn't cheating. I mentioned that i had seen a message where she talked about the time they had sex - he told me that it was during our break (we decided to break up for 2 months but got back together). I believed him and I wanted to stay with him so i said that I forgive him but he then continued with our fight and broke up with me because I was disrespecting his privacy by reading his messages.
I was misrable. I thought i had done something wrong. He manipulated me into thinking i was a bad person for going through his messages.
I was really depressed for a few weeks if not months.. until he came back (about 3 months after we split up). He wanted to be together with me again and I agreed. Until one day less than a week after it finally hit me. He is the one who cheated - it doesn't matter if it was only sexting. While i tried to give him hints i also asked if I was the only person he had ever had sex with and he said yes. So he lied to me either way.
I broke up with him.
A year later he came back again - he needed me and couldn't be without me. I listened to him and said I could maybe try to be with him again. Then he broke my heart again by telling me that he wanted to confess he actually cheated on me that one week. They didn't had sex during our break - it was while we were together; when he told me not to worry about it.
TL;DR Even not good looking guys are assholes. Fuck humanity.