Hello OP - I want to say your post has really resonated with me, especially the DP parts. I have been very miserable as a mother, with two girls and a 3 year age gap. From 1 and 4 to 3 and 6 was absolutely grim. They are 6 and 9 now.
I tried to explain to my DP but, honestly, I feel it was inconvenient to him and his time consuming hobby and he doesn't really "do" guilt. DP also earns probably x10 what I do (both professionals!), though I am PT as we just couldn't manage homework and dinner from 6pm onwards when I was working a longer day.
My DP isn't a monster, he is good fun, generous, makes our dinner every night. No-one is perfect, but he left me flailing when I needed more from him. Even now, I find parenting a boring, lonely and often incredibly stressful experience.
That said, I don't regret having two because despite the fighting (and there is a fuck ton of it) they do play together and occupy each other (and give me long periods of peace now). I love them but I think I am probably situationally depressed by parenting. No point in teaming up with mums who are my friends and their kids, because frankly it isn't much fun and I think I am pestered more?!
The squawking of my 6 year old and her whining are also destroying my nervous system. This week I am practicing saying USE YOUR STRONG VOICE every time...and it seems to be working a little!
Phew sorry it's a lot. Good luck to you xx