Recently lost relationship with someone I thought I would be with forever

Four years ago I (M33) was living in Vietnam as an English teacher and met a girl at the school I worked with who I thought was super cute. She (F28) has just gone through a breakup I found out and I approached her and offered to hang out. We ended up having sex rather quickly and seeing each other nonstop and within a month or so we were a couple. It was a little fast but we had a lot of chemistry and our senses of humor worked so well together that it felt right.

We moved in together in Saigon and had a good 3 years together there and traveled to about 18 countries together. Always laughing and having a good time. Things worked really well and she always talked about how she wanted to have kids with me and all that. It felt like something that was going to work for the long haul.

When we agreed that we wanted to move to the US together in order to settle down and have a family together we started to encounter a few problems. The ongoing argument was where to go when we left. I often asked her "where would you like to move to? I am happy to go almost anywhere but what sounds good to you?" and she would always say "I don't know! Things will just work out" Well, this stressed me out since it didn't make sense to me to leave without having some sort of game plan. This argument came up like once a month for a year before we left and she seemed upset that I was putting pressure on her to even think about where she would go or what she would do. There were times I blew up about it and times I asked and expressed myself gently but still, she would just be like "god I said I don't know. What do you want from me"? It felt odd but I loved her so much I decided to push through.

We agreed to go stay with my parents in Arizona for a few months to figure it out and once we got there she got a little bratty and unappreciative about the hospitality (her parents are well off and she was handed everything as a kid and I wasn't) but still did not want to discuss where we would go and what she wanted to do and the arguments became almost a daily thing at that point since my parents didn't really want us staying forever without having our shit figured out.

Anyhow, during covid she went to Hawaii where she is from for a few months and I gave up and just got us an apartment in Arizona (i didn't really want to stay in my hometown but didn't know what else to do). I started working pretty quickly because I was thinking we might have kids soon in a year or two and wanted to get my shit together. She still didn't quite know what she wanted to do and tried a few jobs and quit. We both became interested in Real Estate investing and it was an idea we both wanted to pursue at some point so she got her real estate license. While she was studying for her real estate license she got really into watching these stripper vlogs on youtube and pole dancing classes and brought up the idea of being a stripper. I told her, of course, I wouldn't feel comfortable with that and she told me I was insecure and controlling and all of that and it blew up into a fight and I will admit I said some nasty shit. I apologized the next day and said I felt bad and the idea went away.

I promise I am getting to the point

Anyhow, we joined this Real Estate investment group that hikes together every Sunday that was put on by this hotshot real estate guy here in town who is in his 40s. We met some nice people and he seemed cool also. We had a nice time on the hikes and enjoyed everyone's company.

Well, in January my ex posted a photo of herself in a bikini on Instagram after doing a cold plunge in her pool and I guess the guy who hosts the hikes invited us to come to his house for a cold plunge. I thought it sounded alright but also I don't care to drive somewhere just to jump in some water. That same month I went to a 3-day seminar and while I was there I got a text from her that she just left his house and went swimming there. I thought it was strange and asked her who else was there and it turns out she went by herself. I felt disrespected by that but I didn't make a big deal about it since I always trusted her and I knew he had a gf. She said she didn't know no one else would be there and nothing happened.

Anyhow, fast forward to April and I am sitting in the living room in our apartment and I opened up her journal which she writes in every day and leaves on the couch. Btw, I never read her shit or snoop but got the urge to look at it this day and read it. Every day there was a comment or two about this guy "ugh I can't stop thinking about Zach" "Zach thinks I am so hot". "Zach wants to fuck me" etc. We get into this huge fight and she hides the journal. A few days later I find it again and read more "Zach initiated with me and I caved in and came this time". I asked her what the fuck all this shit is and she was vague. We just send hearts to each other and flirt. That is all. It didn't make sense and I kept trying to get the truth out of her about it. I called his girlfriend who then confronted him and he called me and admitted nothing physical happened but there were nudes back and forth and sexting but that was all.

She cried her eyes out and begged me to go to therapy and that I was the love of her life and all of this stuff. We went to therapy and I moved out of the apartment to stay with my parents while we went on dates and worked on it. It was hard and there were ups and downs but we connected and I made apologies for some things I had done as well (she gaslit me a little and said I said so many nasty things in the past but really it wasn't often and only once in a while in a bad argument) Of course I didn't think I was to blame but still said I apologized for how some things had gone.

Anyhow, I noticed her becoming a little distant during all of this and started getting insecure and long story short. She ended up sleeping with a different guy (M23) in our apartment which officially ended it. She said I caused it because I called her helpless in an argument or when she wanted to be a stripper I told her she wouldn't make it in real estate or whatever which was super old shit i apologized for anyhow but still I dont think it makes any sense. I still see the therapist we saw together and she told me that this had nothing to do with me and is issues within her. I have no idea but still it hurts. I contacted her ex in vietnam who she was with before me (she said similar stuff about him that she said about me and how i treated her and I figured he could tell me if he dealt with similar stuff with her) and it turns out that me and her hooked up when they had just started a break together and were working on things as well. Also, he met her at their old job, I met her at our job and the new guy is someone she works with which makes it feel like a pattern.

I still love her and of course I could never be with her again but it still hurts. I feel stupid for not ending it in vietnam when i had the feeling to do it but i tried to make it work. I catch myself wondering if she has a mental problem now. I think she is now seeing this 23 year old guy she works with and I know she has always been in one relationship after the other. One red flag I remember is I asked her what her type was and she said "i dont really have a type. just whoever gives me attention" and her excuse for sending nudes to that guy Zach were that she just got carried away with all the attention she was getting from him. She admitted that she looks for validation often. I feel shocked by all of this since we never had these issues and even while being in the states we didnt have many issue other than the few i mentioned. I admit we went out less because we were getting all started up in new careers and both working alot but there was not much communication on what she was missing or whatever so I got totally blindsided and its not fair.

Does anyone have any words of encouragement on this issue? Any thoughts on what might be going on with her? I mean, cheating twice while also crying about how i am the love of her life is pretty crazy. I realized she is emotionally immature and never knew what she wants which is the main cause of many of our arguments and she didnt accept her faults well in the arguments but does this sound like some kind of personality disorder? I am just looking for some kind of answer.