I discovered saved files on my boyfriend's phone. How can I move on from this?

I'm a 27-year-old woman in a five-year relationship with my boyfriend, who is 28. He’s my best friend and we've shared a lot of experiences together. Lately, though, I've been feeling unwanted in our relationship. He seldom initiates intimacy, and when we do engage in sex, it feels like I'm the only one making an effort. As a result, there can be months when we go without it. We see each other every weekend and occasionally during the week. I've raised this concern multiple times; he acknowledges it but no real change occurs. Sometimes he becomes emotional when I bring up these issues, expressing that he feels "not enough" or that I’ve been “too hard on him,” which complicates our conversations and often leaves me feeling responsible for comforting him. Recently, while he was sleeping, I went through his phone (I admit it’s not my proudest moment, but I had a strong suspicion, and this was the first time I did anything like this in nearly five years together). I discovered that he had saved explicit videos of women from the internet in his files, which I found in the Recently Deleted folder. What hurt the most was seeing a screenshot of a mutual friend in a bikini also in that folder. It made me feel sick. It’s not just about him looking at such content; I understand that everyone has their needs, but the fact that he saves it, hides it, and then deletes it tells me he knows it’s wrong. Now I'm overwhelmed with thoughts about how this fits into our already struggling sex life. I'm always the one to initiate, and even when we do have sex, he rarely finishes. It’s led me to wonder if he simply doesn’t desire me in that way anymore, and I've questioned whether I can accept our lack of intimacy for the long term. Discovering that he's engaging with sexual material outside of our relationship only adds to my feelings of hurt. I can't shake the thought that he’s choosing to find pleasure elsewhere instead of with me, and if that's the case, what does it mean for us? I’m not sure how to process these feelings. I'm hurt and feel uneasy being around him right now, and a part of me doesn't even want to be intimate with him anymore. Yet, another part of me wants to understand his perspective and see if there’s an explanation that might change how I feel. I just don’t know what that explanation might be.