Why on earth do people get so aggressive about the OP's personal situation with her DH? Who cares what the rest of the world think about a size 6 or size 14 - all that matters is what OP's DH thinks of HER!
OP, totally understand why you are hurt. It's him nitpicking over a few kilos/sizes, and telling you he doesn't find you as attractive as he once did. Very insensitive!! Is he on the spectrum? I ask, as if he is, then he isn't being malicious. However, he needs to understand how that has now made you feel.
Whatever you do, don't feel embarrassed or ashamed of your body. Have an honest conversation with him that you find his superficial attitude to attraction is off putting. It's one thing if he has noticed a change in size, quite another if it has put him off having sex with you. Are you sure it has though, or did you conflate them 2 issues?
Not sure what to suggest other than this is a good time to focus on feeling good about yourself, and doing everything that entails. If he can't get himself to see your beauty irrespective of size, you can't force it. Hopefully he'll shake himself and realise everything your body has been through to give him his children, and the life he's had with you.
If he doesn't, take a lover. I joke. But if you carry on loving yourself, and not giving two shits what he thinks, you'll protect your own self esteem. The best you can do.
Ps: I'm also a short size 6, with curves. You're absolutely not androgynous or whatever crap people are spouting on here. There's different body frames and figures. But your husband is an arse for noticing the minor change of ONE size up.