Porn is a very contentious subject; I'll be upfront and say I watch it (which is why I was able to list 7 male porn actors off the top of my head) and my partner watches it.
He watches it in moderate and discretely. I do the same.
We tried watching it together once or twice but that didn't really flow and definitely would not now.
So.... While there are many many ethical issues with porn, both personal and in the industry, let's say I'm ok with it ......
I absolutely do not think it is ok that he is searching a out how to "fix" your post breast feeding boobs.
It is immature, superficial, selfish, dumb, objectifying etc. You are not a porn actress.
He married you as you are - if you weren't his type that's his fucking problem. He shouldn't have or he should display some common sense realism, tolerance and kindness now he has and you've born three of his kids.
I am, in some ways, my partner's type. In others I am not. He, very indirectly, let it slip that he'd prefer bigger breasts. I didn't really give a fuck. I'm compromising on things looks wise to be with him too. That's the way of goes, many ppl end up compromising on looks etc if the overall picture is what they want and they like the person, they both want to.conmit etc.
My partner would never ever, in spite of watching a bit of porn, make any comments etc that would suggest he's unhappy with anything about my looks. He knows to stfu. Abd I know to stfu. Not would ge be looking into changing anything. That's what people with common sense and tolerance do.
I was once told an much older ex bf preferred big boobs, and he hinted at paying for a boob job. This man had ED. I shagged my ex bf, who I still house shared with, told him and ended the relationship. Hopefully he learned something. Maybe he didnt. He was an objectifying, chauvanist, love integrity, emotionally unintelligent dick anyway; and this is about your h's character too.