Concerns about trust in my relationship [20F][21M]

I've been in a relationship with my boyfriend for two years now, and sometimes I feel the urge to check his phone. This is partly because I once found a brief conversation he had with a coworker who has made advances towards him in the past, despite my request for him to respect our relationship by not engaging with her. Since then, he’s attended several parties with his coworkers, and he often makes excuses for why I can't join him. Earlier today, I quickly looked at his phone and noticed a picture of a naked woman in his hidden photos. I've also overheard him discussing this same coworker and other girls with his friends. The last time I asked to see his phone after discovering the conversation with the coworker, he seemed very reluctant to let me look at it, and I had to ask multiple times before he finally agreed. Now I'm unsure whether I should confront him again and request to see his phone for my own peace of mind, or if I should try to let it go and stay chill about it. I’m feeling really confused, as I worry that my love for him might be clouding my judgment.