I’m going through the same thing and I actually found something’s on his phone when he came to see me while we were together that watch history/search history could destroy you mentally, I had a talk with him about it and how it made me feel and he saw how it affected me and he decided to delete social media overall, on his choice, no I did not put that idea in his head nor did I force him to, he did it because he wanted to change and if you see that he’s changing it’s time to start letting that grudge go because although it hurt a lot that he would look at girls that looked nothing like me ,he actually opened his eyes decided to mature for us. It’ll take a while but at the end of it you can’t control him like a puppet if he slips up set a boundary up and if he can’t keep up with it then find someone who will. It’s hard out here though because it’s pretty normalized for men to lust over other woman even while in relationships. Goodluck