Bf (30M) likes posts of sexy girls on insta after I (28M) told him I was uncomfortable

Problem/Goal: I want to forgive him, but I can't get all those girls out of my head. It's not really cheating, but he disrespected a boundary. Should I stay or go? If I stay, how do I get over this? All I see are their beautiful faces and breasts, and then him looking, lusting, and liking them. How do I protect myself?

Context: In the first yr of our relationship, I told him I was uncomfortable that he was following ONE pretty model. He said he unfollowed her. In our currently 4th year of our relationship, I saw that in

the 3rd year of our relationship that he liked a girl's pic. She was beautiful and wore a very revealing cleavage where basically her nips could pop out anytime. I was able to see it cause he lent me his phone while mine was charging. I scrolled his insta out of habit of scrolling insta on my phone. I saw majority of the stories at the upper portion of insta are from girls in bikinis or showing cleavage. I was so shocked cause I thought he only followed one girl, turns out he follows more than ten! I checked his liked posts and saw he liked the photo of a girl with the cleavage in the 3rd year of our relationship. I also saw in his messages that he sent a similar girl a fire emoji and then a heart emoji for different photos, which I don't know what the photo was since it was unavailable. Except that her profile pic was also showing cleavage. He also did that while we were together (1st year in) and after I told him I didn't like it. He said he didn't unfollow them except for that one girl I pointed out, but that he rarely checked his insta until that day. He said he doesn't remember what happened, but that probably on that day he opened insta for a final look before deleting it. It might be the first photo he saw and he liked it out of habit. He said he followed sexy girls when he was single. He said it was a mistake that he checked her out when he was with me, and that is why he deleted insta since he knew it hurt me. He did delete his insta around the later half of the 3rd yr of our relationship, cos I would send him insta reels and he said he can't open it. He only installed it again cos I said he should so I can send him funny reels. I trusted him for so long. I never asked for his passwords in social media. I trusted his privacy. And he willingly lends me his phone and vice versa when our phones are charging like that day. It's just that it was only now I REALLY saw his insta when he downloaded it again. I felt stupid not doing a background check on his followings when we first started as a couple. I wanna believe that he just made a mistake of habit, since he did delete insta for a while. He was also insistent on not installing it again, but I only asked him to download it again cos I wanted him to see the funny reels I send him. I never knew why he was stubbornly refusing to. Turns out this was why. I just feel so blindsided. I feel shocked that he was that type of guy that follows sexy girls. I mean I get guys do that. But he follows like 10 plus girls. It's majority from their stories on the stories at the upper part. Maybe some girls are okay with that, but I'm not. I find it bordering emotional cheating. I myself never check hot guys out on insta or worse, openly like it while in a relationship out of respect for him. But it's also just one photo he liked and it seems that he did delete insta for me. My dilemma is that he crossed a boundary when we were three years in and already serious with marriage. And he said he plans to propose this year. We've been talking about the future. I am afraid he might be hiding more. But he seems open about me using his phone. I'm confused. He's so sweet, gentle, patient. He never cheated on me, or so he says. He is a gentleman and buys me gifts. He makes time for me. But he also doesn't initiate much on dates. He rarely chats. We meet only once a week. We call every night. He rarely initiates sex too. It's always me. And I feel lately I'm the only one initiating conversations about marriage. I only knew he plans to propose because I asked him where we were heading.