Bring up what, exactly? Or to put it another way, what is the problem? Is it that he is looking at other girls at all? Is it that they are Instagram models? Is it that they don't look like you? Everyone notices other people when in a relationship. Literally everyone. You can't stop noticing people, nor can you stop being attracted to people. Actively searching out content relating to other girls, whether that be on Instagram, porn or something in between, isn't in and of itself something that should threaten your relationship or cause you not to trust him. Providing it doesn't get entirely out of control, it's just a way of getting dopamine hits. If you have particular red lines or boundaries when it comes to this content, you should obviously communicate those. But it is worth reflecting on why you feel that way. And I think the reason you feel like that way is the "past experiences" you reference. That makes sense, because as I say, in and of itself I don't think this is objectively concerning behaviour. But it does depend on context. If those past experiences cause you to doubt what might otherwise be innocent behaviours than your concern may well be genuine, but the root course is those past experiences and not the behaviour itself. If that is the case, it's worth seeking to address that, either directly with your boyfriend or otherwise. This is a long term relationship, so there is obviously a lot of context, and relationships of this length always have some issues to one degree or another. It sounds to me like there are unresolved past issues in this one, and if they're weighing on you I think you should address them.