We've been together roughly 6 years; 3 married. We've gone through a lot during that time but usually the stressors were external (my toxic family).
So, he recently went back to get his MBA and there's a woman in the group he will be in for the duration of the degree. They become relatively quick friends.
During the program the class takes a trip overseas, I was aware of this going into it but I wasn't prepared for it to be the first 6 months. NBD really, but it unfortunately fell on the same dates as our anniversary. Originally we were going to celebrate our "legal" marriage instead of what we've been doing which is our ceremony to make up for this fact. That unfortunately didn't happen but again I'm pretty easy going so no big deal.
Back to the issue, he tells me that spouse "aren't allowed" to go on this trip, okay fine I could see that so I make no plans to go. We go out for a networking event the school is hosting and it comes up that other spouses are joining. And at this point I can't. I get this weird gut feeling and end up looking at the messages between him and this women and he had deleted a message that basically insinuated that he asked her not to tell me other spouses would be there. We work through by setting a boundary that he doesn't hid things involving their friendship, I at this point do not ask him to end the friendship or stop talking to her bec I'm relatively secure individual.
Trip comes and everything is fine but I keep feeling kind of weird, I end up asking him directly after the trip if he had dinner with her or did any other things alone to which he said no, and I said I thought he was lying. Conversation ends.
Two ish weeks go by and I am literally going insane so I look through his phone again and find photos that prove he did in fact go to a nice dinner with her alone (mind you he loves spending money on fancy restaurants so that's not the problem). I confront him again, and again he lies. Immediately following the lie I called out details and he finally admits to it.
So this happened like a 1.5 months ago and I can't really see him the same anymore. I am torn up that he would lie, the first month he took almost no accountability and I was literally on the verge of leaving. He's gotten better but I still feel unsure about what to do. I don't think he physically cheated either but lying directly to my face and breaking a boundary has been very hurtful. And I don't feel the same safety and security I felt before.