Air - I think what you're feeling is normal. I spend my nights walking between bed and cot with sleep deprivation and an all out certainty that I'll never sleep again, and what's the fucking point because no-one understands, or admits to understanding the resentment. Then DS1 wakes early because of DS2, and spends an hour thundering between bed and toilet for Something To Do because he knows it's not time to get up.
I had PND with DS1 and it was awful. I was functioning, but with constant intrusive thoughts. I would have hallucinations on a night with night terrors, and would often fight myself to not head out in the car and drive under a tractor. I'm petrified of it happening again, and read too much into my thoughts now, trying to identify triggers.
What I tried to say in my other post is that the thing I find hardest with kids and depression (singularly and together) is that it feels like a sadistic/masochistic love in some ways. When DH keeps me awake all night snoring, I can kick nudge him, get stroppy, make him go elsewhere. It's not his fault he snores, but I've no bloody patience. If he didn't feel like sleeping one night and disturbed me by chatting or whining that I wouldn't entertain him, it'd be unacceptable. I certainly wouldn't want anything to do with him the next day.
And yet with DS2, he keeps me awake when he doesn't want to sleep. He will wake me for food, then decide he doesn't want any. Like the snoring, it's not something he can control - but I also "can't" feel the same resentment I would towards anyone else. And I still have to play and care for him the next day, even when I feel half dead.
I feel I've wittered in sleepy delirium...