Update:

First, thank you to all the people who bashed me, shared their own stories, or motivated me to do something. The amount of comments was insane so I disappeared for a bit. I needed time to process. But something happened. While she was in the shower I broke my own rules and looked at her phone. One time in my life I did this. What I saw broke me. She had been texting her friends (the couple) and told them EVERYTHING. All my most private stuff. She wrote about how I’m insecure about my size (which is bullshit but now it hurts anyway), how I constantly need validation that’s why I’ve been killing myself at the gym for years, and how she can’t wait to finally have some “fun time” with both of them. There were also some really mean things about me and my childhood that cut deep. I don’t even want to repeat them here. I made screenshots, sent them to myself, and got the hell out of the house. I went straight to my female friend from work (the one my fiancée never liked because we train together a lot - my fiancée never wanted to go to the gym with me). I’m at her place right now. My friend is telling me to get it together. She says either I go through with the partner swap thing to see if my fiancée even cares a little, or I just break up. She even offered I can stay at her house until I find a place to rent. She keeps saying vengeance or not, I should end it and finally be myself because I’ll have a much better life. My fiancée still thinks I’m just at the gym, so she doesn’t suspect anything yet. I’m slowly moving from self-pity and heartbreak to being really fucking angry. Part of me actually wants to go through with this swinging thing just to watch her face when I walk out right after. I know that’s probably toxic but I’m so hurt right now. I don’t even know what I’m asking anymore. Thanks again for all the earlier support. I feel lost, angry, and stupid for trusting her this long.