I know exactly what you mean.
I'm frayed at the edges now, trying to work full time and look after the kids - and all the help we've tried to buy in (cleaner, nanny, after school club/whatever) has only slightly worked in that it's just flaky round here - cleaners decide not to bother turning up, nanny the same, after school club cancelled with 15 mins notice (even if available) etc.)
I've told DP that I'm going to wind down my job, and that if he takes a promotion that's on the table, I'm going to stop working (although I'll keep my hand in in a hobby capacity - this is possible in my line of work) because it's doing none of us any good. I might even consider a 3rd kid if that happens.
BUT having said that, the thought that he'll then feel justified in expecting me to pick up his socks (at the moment he's just lazy about it - and that's not a good example to the kids) is one that doesn't sit well with me. Some firm boundaries will need to continue to be enforced. I'll be home for my mental health, and the good of the family, not to be his personal skivvy.
What has helped now, while I'm freelance? Disappearing - leaving DP with the kids when he's home and I need to work - either shutting myself in a room and refusing to answer, or preferably actually leaving the house. Ignoring stuff (shut the door and ignore clothes everywhere, breakfast stuff un tidied etc. - I'm at work, it's not my problem). Making sure that DP has assigned tasks and does them (taking kids to school, putting them to bed) - no skipping a day and assuming I'll take over without pre-arrangement. I do have a timetable for the kids, and if DP misses a sports day or performance, that's his problem. If he feels left out, he has all the tools available to him to be involved that I do.
Above all, I've cultivated a blazé attitude - I'm important, I'm involved at work and at home, but I'm not servile about either. If I have to start work late, I inform my colleagues, I don't apologise for it (I'm freelance, so I can). If I don't clean something (ha! Perhaps that should be 'When I don't clean anything') or dinner is from the freezer, then it is what it is, I didn't have time - and my time is as valuable as anyone else's.