AITA for Catching My Boyfriend Sleeping With His Coworker in Our Apartment After He Lied About Working Late?

I (27F) have been living with my boyfriend (29M) for two years and I thought we were stable until I started noticing small things that didn’t add up like him muting his phone when I entered the room and suddenly working late shifts that his schedule didn’t reflect. My closest friend (28F) who works in the same company as him mentioned she had seen him getting unusually close with a new coworker (26F), but I brushed it off because I trusted him completely. Last night I told him I would be staying at my sister’s place (25F) after dinner, but I actually returned home early because I forgot my work laptop. When I opened the apartment door, everything looked normal at first, except his shoes were not where he usually leaves them. I heard movement from the bedroom and assumed he was just changing, but then I heard a second voice whispering. I walked closer and pushed the door open slowly and saw him sitting on the edge of the bed with the coworker beside him and they both froze when they saw me standing there holding my keys.

For a few seconds I just stood there holding my keys, trying to understand what I was actually looking at. My boyfriend (29M) didn’t speak immediately, he just stood up too fast like he was trying to create distance, while the coworker (26F) pulled the blanket over herself but didn’t leave the bed. Nothing about it made sense in a calm way, because it didn’t look like something had “just happened,” it looked like something I had interrupted mid-conversation. My first instinct wasn’t shouting, it was asking him to explain why she was in our apartment at that time, and why he had told me earlier he would be working late at the office.

He started saying it wasn’t what it looked like, which I think is the most predictable sentence in situations like this. The coworker finally spoke and said she had just come over because she needed help with something work-related, but she couldn’t explain why she was in our bed. I asked her directly how long she had been coming over when I wasn’t home, and that’s when she went quiet. My boyfriend tried to step between us and kept repeating that I was misunderstanding everything and that I should calm down, but the more he spoke the less it matched the situation I was looking at.

I told him I wasn’t going to argue inside the bedroom, so I stepped back into the living room and asked them both to sit there and say exactly what was going on without interruptions. My sister (25F) called me at that moment because I had texted her earlier that I might come home, and when she heard my voice she asked if everything was okay. I told her to stay on the phone. My boyfriend looked increasingly nervous at that point and started saying I was involving other people unnecessarily, but I told him he should have thought about that before putting me in this situation.

At that point I realized arguing wasn’t going to give me anything useful, because he kept changing versions of what happened every time I asked a direct question. The coworker eventually admitted she had been coming over more often than I knew, usually when I was “supposedly busy,” and that they had talked outside of work multiple times. She insisted nothing physical had happened, but even that didn’t match the way they were acting or the secrecy around it. My boyfriend kept saying it was just emotional confusion and that I was blowing it out of proportion, but I told him emotional confusion doesn’t require lying about your location.

After that I asked both of them to leave immediately. My boyfriend tried to argue that he also lived there, which was true, but I told him I didn’t feel safe sharing the space anymore after what I had just seen. My sister stayed on the phone the entire time while I packed a small bag for him and left it by the door. He eventually left after about twenty minutes, but not before saying I had ruined his reputation by not handling it privately. The coworker left first and didn’t say much after the initial confrontation.

Afterwards, everything felt quiet but heavier. My sister told me she had suspected something for a while but didn’t want to accuse him without proof. My closest friend said she wasn’t surprised, which honestly hurt more than the actual moment. Since then, my boyfriend has been telling mutual friends that I invaded his privacy by walking in without knocking and that I should have waited to talk to him calmly instead of reacting immediately. Some people in our circle think I should have handled it differently, while others say I did the only reasonable thing in that situation.

So AITA for walking in and exposing what was going on instead of talking to him privately?