My bf (29) and I (F28) have been in a long-distance relationship for 4 years now. I love him, he's my best friend, and quite honestly the only person I have ever felt comfortable enough to be myself around, or ever truly loved. He makes me feel cared for and appreciated, he's met my family several times and we even traveled together. His family knows about me too (he told them hesitantly a few years in). My family already treats him like their SIL (we planned to get married) but I have never met his family or have any kind of communication other than formal Happy Birthday texts (which already makes me insecure that I'm not as involved in his life as he is in mine). I share everything with him and I was under the impression that he does too but I was wrong.

He got a job last year and things sort of changed between us. I don't know how to explain it, it just started feeling off. Just a gut feeling. He wasn't as obsessed with me as he used to be and I told myself that it was probably because of his long hours at work. All this while, he would share stories of his patients with me and some minor interactions with his male colleagues here and there but never a woman. I also noticed that when he'd come over to stay, he'd put his phone upside down, carry it to the toilet, during a bath, etc, and quickly hide a notification if I was around, he never did that before. While apart, I noticed that he would stay online on WhatsApp late at night for hours sometimes after telling me he was going to bed. This went on for months and I kept getting paranoid. I didn't address it directly but I told him I've been feeling insecure about us and I don't know what to do. He'd just laugh it off saying I'm worried over nothing or tell me he doesn't know what to say.

Getting more paranoid without answers or any solid reassurance, I checked his IG following and found out he follows a lot of girls from his college/work he never speaks of and constantly likes their thirst posts. This is one of my pet peeves and I find it really disrespectful. One night when we were sleeping, he forgot to put his phone under his pillow and I went through it, even though I absolutely dreaded doing so and hate myself for it. I found out he had been secretly texting a girl from work I never heard of for almost a year. And not just work talk, they were flirting. Like, she told him she saw him in a dream, he told her her eyelashes are naturally curled, she looks good, sent her one of those "send it to someone who's cute" memes that he also sent me, she told him whoever is close to him is really lucky, that she could sit and talk to him all day and he said "same", she told him she was shifting and he offered to come over and help her saying "you're so slim and fragile, how would you move on your own (roughly translated to English from our native language), she told him he notices tiny details about her and knows her so well in such a short time, and he should stop paying so much attention to her (like notice the color of her earrings) with a bunch of 🙈 emojis, and he replied saying he has "eye for details 🙃" . He also told her that he feels "alone" even though he's surrounded by people, sent her a post that said "Send it to the best person you met this year". There are also a few where she asks him to go out together and he agrees. They were texting late at night too and when he was with me. But he never once mentioned her to me. And the funny thing is, in all the texts I saw, he never once mentioned ME to her.

When I confronted him, he apologized a million times. Cried and swore to his mother that they were just friends. And that he told her in person about me several times. He told me they never met outside of work, even though he said "yes" over texts because he didn't want to be rude, and he didn't tell me because he thought it would make me overthink over nothing and raise issues between us as we are long distance. They became closer after that and then he got scared that if I found out now, I would definitely think about it "negatively" as it may sound inappropriate. And that he was going to switch jobs in a few months so they would have lost touch anyway (pisses me off to think that he was planning to NEVER tell me about it). He cut all contact from her now but I don't know if I can trust him again. I also saw that his fyp was full of naked women and OF girls. To which he said that they appeared after his friends sent such posts to him as a joke a few times and he stopped using IG much because of it.

He begged me for another chance but I don't know what to do. I can't stop thinking about it. Am I overthinking or blowing things out of proportion? Was what he did acceptable? There were no sexts or pics or more flirty compliments but I can't shake the feeling that if I hadn't found the texts when I did, he would've cheated on me or broken up with me later. And, that if he can flirt secretly for a year, he will do it again in the future. He says he didn't know what he was doing was "flirting", he was just being "nice" to a colleague who was senior to him at work first and then they became "good friends". Is this not flirting or emotional cheating lol? And, he also admitted that some things the girl said made him "uncomfortable" and she even tried to ask him to go out to grab food or something a few times after work but he turned her down respectfully, but she did it again and he told her no and that his GF would kill her. She also has a boyfriend. Sounds kinda like damage control now but idk. Every couple of days I have a breakdown because of this and it's making me miserable. He watches me get sad and frustrated but never says anything. Just cries and keeps quiet or tries to distract me by doing something sweet for me. He says he's overwhelmed by emotions doesn't know the right thing to say and is scared of making things worse and losing me.