Brings up anal all the time - tell him to stick a dildo up his ass and see if he likes it. I've tried anal and at best it's meh, feels like nothing and at worst painful,bloke a bad, burning case of diarrhea.
Its all over porn now to an extreme degree, but as far as I'm concerned bits all about/for the man and nothing for the woman (of course porn actresses fake that it's great but that's their job, god love them).
Seems like some men don't feel they're getting it all the ways they should be unless they're sticking it up someone's ass. Well,nno pun intended, but fuck them; they're not hassling me for something bi get nothing out of. There's no clit or g spot up there, it's about hoke, not an in hole(!)
So, not to put too find a point on it, I'd tell him to shut up about it and stop trying to push some porn originating fantasy onto a real woman, how much porn is about the women's (true,) arousal and enjoyment; sadly very very little. It would be annoying & selfish even if you weren't pregnant; but pregnant it seems even more inappropriate/shitty (again no pun intended).
That rant aside, and on your main point - I don't know why someone would go looking at porn not long after sex other than that they're still horny (and perhaps that the relatively conventional sex didn't fully hit it for them). If they're still horny and don't want to 'bother' you further, I suppose that's understandable. The content is unfortunately not unusual in porn, but as I said, i'd make it clear that it can stay in porn. If he leaves for not getting anal, he wasn't worth having.
As for asses .. we all find different physical things attractive/sexy, sometimes things are partner doesn't have; it's not a prerequisite or important, it's just fantasy/sexual. Bi know I don't have every physical trait my partner finds attractive, and I know he most certainly doesn't have every physical trait I find sexy/attractive. A partner encompasses more than that. Does it really matter all that much if they fantasise about that physical thing, it's in the realm of fantasy/masturbation.