You could have been describing my marriage. I've been separated 2 years now. DH and I were fantastic friends, I described him as my best friend and we I thought worked great together, until we had children. Both were very needy as babies, I took on nearly all the mental load of raising them, I felt like everyone relied on me to manage everything, plus working as a teacher, full time. He was like having another child. We recently had our 12 year old diagnosed as ASD and he's finally admitted he has traits, they are very similar.
Resentment set in big time, we did have moments over the next 10 years when I fancied him or we had really good periods, usually on holidays or when we were away doing something different. But day to day life with him was more difficult. He drank a lot and admitted during counseling that he'd not been happy for about 3 years.
We did try counseling, my heart wasn't in it, and I had my head turned by a friend I started having feelings for. Not proud of that at all but I was just so miserable and felt so unsupported. I ended the marriage this time 2 years ago during lockdown. It was horrible for months, but we are all in a much better place now. It's not easy, there are days when I wish we'd tried a bit more, when I worry about money and the future, the divorce etc and think was it worth it ..but then there are times when he's still thoughtless and unsupportive with the children or cold with them, and I know it was the right choice. He still relies on me, I still do all the work, the organisation, etc, but I do it so the kids have an easy transition to staying with him 2 X a week. I grit my teeth when he asks for lifts, or asks me stupid questions he could easily find out himself. He barely contacts them in between visits and whilst that suits me, I feel for them that they know their dad doesn't really consider that important.
I'm with the friend now, only been a few months, but the difference is astounding. He asks about my day, and wants to know, he asks about the kids, he listens, if I'm upset he notices and asks me what's wrong. That's in part because we don't share a home or responsibilities but see each other on our own terms, twice a week. Life is easier when you know you have yourself only to rely on.
I'm skint, I may have to sell the home I love, but we are managing and the three of us together have a lovely life. Yes it could be easier with more money, with more time to myself (I've had to give up running as I just can't get out of the house, and mine are 7 and 12) and I have family nearby who help a lot, so I'm lucky.
However, I would advise that you try counseling, try to make it clear to him that it's serious now, because I feel guilty and I do regret that I didn't try harder at the time, or speak up earlier before the damage was done. Life would be easier if we'd sorted out or problems early on when we had babies. But at the same time, I know we did our best with what we knew then, so to some extent I think we did all we could.
Good luck, it's so hard when you realise that having children just changes your relationship totally. It might get better, it really might, but it's also ok to realise if it's run its course. ExDH was devastated when I told him I couldn't do it anymore, but after a week of 'trying' he thanked me for doing it, as he said he never would have had the guts to. We get on ok now, although I often mutter twat under my breath as I drive away after dropping off the kids 😬😂 but it's better than doing it in front of them when we lived together!