Context again: Girlfriend is nonbinary, and uses he/him pronouns. Was assigned female at birth so no risk of pregnancy or anything with us. We are both lesbians.

I fucking hate cheaters. My dad supposedly cheated on my mom about 8 years ago. I say supposedly because to this day he maintains that he's innocent and I have no idea which one is bullshitting me and which one is being honest. It doesn't really matter. What's done is done. I now have a lifelong fear/obsession with being cheated on. It occupies my thoughts at all times. I literally just cannot be normal about this.

Girlfriend has been mostly very patient. Kind of. There are times when he gets very indignant if I try to talk about it with him and other times that he's very patient and breaks down my fear with me in a very caring way. He explains that being accused of cheating constantly, especially knowing he hasn't done it, is exhausting. He says he feels that I don't even trust him at all and when relationships are supposed to be built on trust that not trusting your partner can cause serious problems.

Perfect example: last night my gf got a text from an old co-worker. He's 35 (far too old for my girlfriend), a man (my girlfriend is a lesbian), clearly hasn't kept consistent contact (thought my girlfriend was dead and asked my mom about it when he saw her wearing a shirt with my girlfriend's name on it), and has a girlfriend of his own (on and off again but they seem to really care for each other). All signs point to this not being someone my girlfriend would cheat on me with.

And yet my stupid, paranoid fucking brain saw that he messaged him on snapchat with "whats up" and immediately began looking for ways to explain how my girlfriend was cheating on me. I had a complete breakdown. He even showed me the message he replied back with, "nothing much, about to go to bed lmao just started a new job and I have to be up at 7" or something like that. 

My girlfriend has his own trauma around people reading his texts - he grew up in a violently homophobic household where his parents would rip his phone out of his hand, go through his history, look at his messages, and peer over his shoulder to try and catch him being a lesbian. This was exhausting and traumatizing and something that freaks my girlfriend out to this day.  He will even hide his phone from my parents if he thinks they're coming up behind him. It's just what he does. 

So this is very difficult for him. I am constantly asking for reassurance via seeing his message or whatever he's looking at. He showed me the first two messages with the old coworker but eventually he was like "enough is enough" and did not show me the last one. He explained that this was about privacy and the fact that everyone was entitled to privacy. That even when you didn't do anything wrong, you are still entitled to not let the cops into your house. 

This has happened so many times w/ so many different people and eventually I realized that my girlfriend was cheating on me with none of them. This is literally like the 11th or 12th person I have assumed he was cheating on me with. And out of all of them, probably the least likely? I mean like I said, this is a 35 year old man with a girlfriend who is clearly not in close contact and my girlfriend is a 20 year old lesbian. 

I still don't understand. Like logically, I can see how my girlfriend is entitled to privacy as everyone is. But I don't understand that, if nothing bad is happening (as nothing has happened prior), then why does he still hide his phone?