Is it possible for a man to be attracted to Both plus size ladies and slim firm young things as well? Or is he just too polite to tell me he prefers slimmer women? I love him deeply, but struggle to get my eating under control!
Of course. Depends on the woman, and her shape.
But you're also making the biggest mistake many women make on this topic. You're confusing the purely lustful way your husband looks at an "actress" in porn, with how he views you. Those two points of attraction don't often converge.
Would your husband necessarily seek out porn featuring a woman who looks like you? Nope. Most people wouldn't. The Halle Berry and Brad Pitt's of the world aren't drooled over because they look like most people's SO and spouses. There is a stark difference between fantasy and reality, and most people understand that. Your attraction to the person you love runs so much deeper than the surface, and that is what enables someone to love a person through expanding waistlines, sagging, aging, and other changes.
If you suspect that your husband however is becoming less attracted to you with weight gain, then just ask. I'm not going to lie to you and tell you that all men are fine with copious weigh gain, because that would be a flat out lie. But If he seems sincere that he is still attracted, and still seems excited to sleep with you, than take the man at his word.
People who suffer with body image issues, like you, often assume that their own disgust with their bodies translates to those around them. Try not to do that, because you could be very wrong.