What should I/we do?

Ok so me and my boyfriend have been dating for over a year. last week i looked at his phone for the first time and saw some messages from this girl i know he talks to , but it didnt appreciate them. Instead of going straight to him, i went to a close friend afraid of starting a fight with him. Well a few days later, my bf found out through my close friend's bf, who is good friends with my bf. My bf has not really talked to me about it and it has been about 4 days. All he has told me is that he is upset and hurt i didnt go to him first about it, and i understand that, and he keeps telling me that i dont trust him, when i do. I just need help to figure out what to do. I understand i made a mistake about not going to him first. But this is the first time I looked at his phone since we started dating and he doesnt believe me. Help!!