I have TERRIBLE body image issues. So bad.. I dealt with food issues also, but never had a full blown eating disorder and that was hard enough on me, I couldn't imagine going through what you did. First off, PROPS to you for not binging and purging during your pregnancy. That takes SO MUCH strength, more than most would understand.
Second, although I don't consider it cheating, I find it hurtful.. I don't have tiny boobs, but mine are average. A big B at the least. SO is ALWAYS looking at "huge tit pics" on his phone. Like daily. I smurfing hate it.. I'm not saying like D or DD boobs either. Like GGG size tits. It's gross. I hate it because that is NOTHING like me. I'm 120 size 32B size 3 and total opposite of what he looks at so trust me, I can totally relate. He does still say I am beautiful and that he's attracted to me, but it still hurts. So I know what you're feeling.
It's hard, but unfortunately guys are visual. Just because he likes looking at that stuff, doesn't mean he'd choose it over you. It's hard to think that way, I know. But try not to read too much into it and drive yourself crazy. He should have comforted you about it though. Feel better hunnie and don't stress.
Yes, those girls have nice butts and perfect bodies, but they're not carrying his beautiful child and giving him one of the best gifts he will ever receive.