Why do i still not believe him

In the past and by pay i mean earlier this year and last year ahaha my partner was following and searching instagram girls who are naked or strippers and even had some on snapchat that he says his friends sent them to him ( still never deleted them though ). I’ve told him multiple times i don’t like it because i’m super insecure especially after a baby and i think it’s disrespectful. Anyway he continued to do it after me saying no and i was the playing on his phone ( we let each other go on eacothers phones) and saw them that’s how i knew. I screenshot them on my phone so i could bring it up later because we were going out with friends that night but when i went to bring it up they were deleted. For 4 days he made me believe my phone was just playing up and he didn’t know what the photos were because i didn’t even get to tell him, until one night i got so angry about it i said you deleted them didn’t you and he said yes. It hurt that he lied and that he did it again after me saying i didn’t like it. Months on and i still cannot trust him, like i will be on his facebook and a naked girl will pop up and i’m left wondering if he just added them or it’s from when we weren’t together. I truly love him but we are getting married next year and i’m just worried he’s going to break my trust again. Any advice or help? I know he loves me though because he treats me right in so many other ways

Please don’t tell me to leave just because i’m insecure or that i don’t like him following naked girls because every relationship is different and i just find it disrespectful and before we made our relationship official he knew my thoughts in no strippers or how i thought these things were disrespectful. I’m okay with him glancing at women out in public but not going out his was to search and follow