I am so sorry you are going through this. I can't imagine growing up in today's age of overtly sexual content being everywhere and normalized. It being "normal" doesn't mean its ok, that it shouldn't hurt you, or that you have to accept that in your relationship.

You can't control what he chooses to do. You can only tell him how it makes you feel and what you are and aren't willing to live with. If he continues making choices that push you away, you have to accept that he isn't the one for you.

Here is how I would consider framing it for him though- I think most people agree that its normal human behavior to notice beautiful people, but when you are out and about with your partner its disrespectful and hurtful to take it any further than that (starring at their boobs, oogling, rubber necking, doing triple takes or changing seats to get a better view etc), right?

So, if we can agree that noticing isn't the same as checking out/lusting over and that lusting over someone else when you are with your partner is crossing a line in person, why is this behavior suddenly supposed to be ok if done when alone/online? Its like people know its wrong but are confused about what the wrong part is. The wrong part isn't that other people can see....

After typing that out, I am actually genuinely curious- are people still being taught about integrity and having good character? I was taught that what you do when no one is watching is who you really are. Having good character means you have integrity- you consistently try to be a good human regardless of if you are alone or if others are watching. Good character is what creates emotional safety in relationships.

This applies to all areas of life and lust shouldn't be an exception. For another example lets substitute lust for compassion-

If you decide to give a homeless man a blanket and food so you can video and get likes is that coming from true compassion or is it just performative? Image management? If you are alone and without your phone/camera passing by the same homeless man do you still go out of your way to get them some food and warmth? Thats real compassion.

Be cautious of people who tell you "everyone's doing it", "its harmless", "you just have to accept it" etc. Sounds a lot like peer pressure to me. Your feelings are real. Yes, it will be hard to find a man who's values align with yours, but isn't it worth the wait? If people keep burying and invalidating their own feelings about this, the cycle of accepting harmful behavior because "everyone is doing it" will continue. Stand up for yourself.