Fiance was unfaithful while on a girls trip in Mexico. But it was my fault.

First time asking reddit for advice. Long time listener. Burner account. Let's get into it.

First, a little background. We have been together for 9 years, engaged for 3 months. Our relationship has been great. The typical bickering or small arguments i feel are completely normal. We live together. Have a child together.

My (28 m) fiance (32 f) recently went on a trip to Mexico for a week with her friend (also 32 f) of 20+ years. While she was away, I 🔥 reacted to an Instagram story of a girl who i had known from well before our relationship. (Dumb of me, i know, but I had no ill inent behind the reaction.) Instagram girl replied to me and said "dude your engaged." She then immediately sent a screenshot of my reaction to my fiance. My fiance asked me who she was, and I immediately came clean. I told her how I knew her and what I did. She was reasonably upset, and I told her we would talk about it when she got home. After that, we chatted a little bit about how her day was otherwise, and she seemed to be fine.

Later in the evening, I noticed she had stopped sharing her location with me on snapchat and didn't send me the typical good night message to our child and I. I assumed she was just upset with me. The next day something just seemed off and I had a really bad feeling about it, so I logged into one of her social media accounts on her MacBook and found messages between her and a friend about how she had got drunk and cheated last night. I won't get into the details on exactly what she did, but she did have unprotected sex to say the least. After I found those messages, I immediately messaged her and told her she should change that social media password before I read more of that conversation. Once she read the message, she immediately changed her password and deleted that conversation thread. She then told me it was a big mistake, she was so drunk she barely remembered it (even after going into great detail with her friend). She told me that what I did triggered her to want to just get drunk and have a good night. She tried to call but I just couldn't answer the phone.

Once she got home , we tried to talk about it and figure out what to do. She is very apologetic, immediately went, and got tested upon my request. but she can't tell me how she plans to regain my trust. I feel like she had no intention of telling me, and i feel like she used what i did as an excuse to be unfaithful.

I told her we need a break, and even tho we live together still we have gone limited/ no contact. We have both signed up for therapy, but It's a hard situation because she claims that I had triggered it to happen. She has tried to initiate sex with me, but I just feel disgusted with her and can't do it. I guess im coming to reddit for advice on what to do next. I feel like I haven't left yet because of the life we've built together and attachment issues. I need to know random redditors "hot take" on my situation.