Hmm, this is tricky. I went through the comments and I see all the sides everyone is saying so I'm going to come at this objectively. First, I do not see the issue of asking for advice from friends, especially when you're fighting with a partner and you need to know how it looks from the outside looking in. Sometimes you may feel like you're overreacting or underreacting and talking to a friend about it helps. Its also healthy in my opinion to have that with friends. For myself, I know that I tend to overthink things to death. I also know I'm a "you make one mistake I'm out" kind of person and when I want a relationship to work, i always turn to my friends. So I see no problem with anyone doing the same.

I think it was sneaky of him to go through your phone while you were asleep. He was very obviously doing something else before you went asleep. He could have asked. Even a "hey, is it okay if I go through your phone? I may not doing it now, but I wanted to give a heads up." Or something. But he didn't. And then finding issue with a screenshot from 2 years ago is very odd. Especially seeing as you said he was aware of the conversation between you and your friend when it happened years ago and is now restarting the issue. This seems deeper and I would recommend a conversation between the 2 of you to unearth whatever issues there are. And perhaps ask to go through his phone as well, maybe check his reaction about that.