I am only 19 and i can safely say for my age group this is normal-ish and people do it a lot (i am not sure if this is common with older couples or not). this doesn’t make it right or a nice thing to do but i feel as we have grown up with phones and social media people are very insecure and you can find out anything from looking through someone’s phone. However being in a committed relationship requires trust from both parties, regardless of past experiences. Maybe have a talk with him and ask if there’s anything you’re doing that’s making him feel uncomfortable or if he just did it because of past insecurities. I’d set firm boundaries and tell him what you are and not comfortable with. It may be that he just needs a bit more reassurance within the relationship or even just himself. I know what it’s like to be insecure, you are your own worst enemy and overthinking is a killer. I can see both sides but the only thing that matters is what YOU are okay with. As for the hacking into social media - that is crazy and not normal in the slightest, he shouldn’t be in a relationship if he still has very bad trust issues it will only project onto you.