From what you say it's not just that's he's put on a few lb. It's that he hasn't put in any effort in the last 10 yrs, he's stood still while you've not. And you don't like what he has become. It's not that you're not attracted to him, he's a totally different person, one who doesn't care, about you, himself, the children, or anyone else, he doesn't try, he has no drive, no determination, no get up and go, with you or the kids.
When all said and done, It's not attractive 😕 if you were single and dating, don't lie to yourself, you wouldn't choose this man.
That's not being unkind, it's about realising that actions have consequences, and he needs to be made aware that his actions are having a very real impact on the way you see him.
That's not a bad reflection on you. A wedding ring isn't one that ties you for life to another no matter what they do. A. wedding ring is the intention that you want to spend your life with another. That means you have to put some effort in to remaining to be the person your significant other wants to be with.
I feel like since we got married my husband has totally stopped trying to look after himself...
I guess I feel kind if resentful as I feel he's pretty low effort with the kids, romantically, even at work and just doesnt care about maintaining good health and relationship.
I think he may be depressed but he won't seek any kind of treatment.
his belly in particular is very large I feel physically crushed
he also doesn't hold himself up if he's on top and his stamina is low
he just kind of gives up exhausted halfway through
Stop having uncomfortable sex, stop being crushed and crying alone afterwards. Start the very hard discussion that he has to make some changes, and that you'll support him or it's the beginning of the end for you.