Op l do understand , l had 2 under 2, but what saved me were strict routines, non negotiable, nap times strict bedtimes etc.....
work out how you want to structure your day around them, set up ma timed chart in the kitchen, talk them through it if they are old enough to understand and implement it ruthlessly!
Mine were always in bed by 6-7.30 depending on age so evenings were the essential relax time for me.
If you spend some time on this now it will really help.
Also can you eek out a bit of money monthly to pay a daytime babysitter, a day or 2 a month and you go and do something just for you?
We missed holidays for 3 years, so l could have a day a fortnight child free from 9-5pm, to get a dentist appointment, see a friend etc.
My DH has never helped at all ever....as he works long hours and travels a lot too, so l felt justified in having some little relief sometimes.