Concern

Everyone's given pretty good advice, so I'll just add this:

Porn preferences and in life preferences very rarely are actually the same. Most individuals know that porn is a fantasy, not reality, and it doesn't mean that he wishes you'd be like girls in porn. It doesn't mean that he doesn't find you attractive, or want you.

Think of it this way - finding your favorite actor or actress attractive doesn't take away from the relationship you have. You can find Chris Evans to be the sexiest man you've ever seen (no lies detected) and also be desperately in love with and attracted to your partner who looks nothing like Chris Evans (or whatever actor you feel strongly about. I just think Chris Evans is pretty!)

If him watching porn in general upsets you, then you need to have a conversation. But if your biggest concern is that you don't look like the girls he was watching - well you also need to have a conversation, but a different one. Be honest, if the former, let him know that makes you uncomfortable. If the latter, let him know that it makes you uncomfortable because you're worried about his expectations of you. If he loves you (which, given that he asked you to marry him, I would think he absolutely does), then he'll understand and you'll probably grow closer because of it.

I agree with others that it would be good for you guys to talk about this. Also, I don't think the things he's searching for are abnormal or anything to be concerned about. Sometimes when people are looking for porn they get sucked into a rabbit hole and stuff they maybe wouldn't normally consider searching for can seem really hot at the time lol. I know for a fact that if my fiancé and I watch it separately we watch totally different things and it rarely has anything to do with each other and what we would expect for our own sex life. We've decided that watching together as part of our own bedroom routine doesn't help anything, it's just a personal thing we both do when we're alone, so why not explore the things we know the other isn't into during that time?

As others have mentioned, if you're uncomfortable with him watching porn in general then that's a totally different conversation you need to have. Even if he's your first, this is so important to talk about in a relationship where you're planning on spending the rest of your lives together. Let him know that you're worried about any expectations he might have because of it. I think most level-headed guys understand that what they're watching and what happens in person are totally different and most would prefer the actual thing no matter what lol. One last thing, I don't know how long you've been together, but he's probably been watching it the entire time you guys have been together, and none of that changed him wanting to propose to you and marry you.

It's been a while but, I now, better understand what you mean. I just needed to mature a bit.