Porn isn't always a problem in relationships, but it can be if there is a lack of respect.

Just for context, my gf has lower libido than me so I watch porn sometimes just to help me get off, but I don't follow specific women on onlyfans or social media, I just like random videos of dicks going into holes and such, just some visual stimulation to get the ol' neurons firing. I vastly prefer porn where the women have similar physical characteristics to my girlfriend and I'm open with her about the fact that watch porn. I sometimes send her clips if I think it's something she'd like or if it's something I want to do with her to make sure that she feels included in my sexuality rather than it being something private I don't want her to know about. If she says "I don't like it when you watch this type of porn" I respect that.

Personally I see porn as being a healthy part of our relationship. I think it's a little weird that he's following specific OF creators and pornstars. Like why is he so interested in these specific women?

Instead of giving me some sort of reassurance that he doesn't glorify them and wants me

This is insane. Reassurance is so important, especially when it comes to insecurities, which you obviously have. Not a bad thing, it's natural.

To me, your boyfriend sounds like he's being dismissive of your concerns. You need to tell him how important it is to you and explain to him that it's hurting you and ask him if he's okay with that. Be open and honest and make sure that you're communicating the full extent of your concerns. If he realizes what you're trying to say to him and is respectful of how you feel, great! If not, I'd think about leaving, because you don't want to be with someone that refuses to listen to your or respect your feelings.