Ok, maybe not what you want to hear and based on my experience and that of friends….
I reckon pregnancy lack of sleep “ trains” you for when baby arrives . If you’re BF you’re going to get woken lots in the night, and if you have a baby that is colicky or just a poor sleeper, you’ll be awake with them for an hour a time or even more. and it’ll be 3-4 years before you get uninterrupted sleep again. For me I Got very worked up during pregnancy worrying about sleep. I’m sure part of my PND was sheer sleep depravation. I never really got back to a full uninterrupted 8 hours after 2 dc and 7 years of broken nights whilst they were young
and then that trains you for waking lots with perimenopause- night sweats, restless legs, or even stupid overwhelming anxiety in middle of night. And then bladder issues again
i used to react very badly to not having 6-8 hours uninterrupted pre kids - very short tempered, frazzled, believing that I could not cope.
but By the time I was premenopausal and having to hold down a job that included regular international travel included sleeping in strange beds and jet lag, I realised I can function adequately on as little as 4 hours sleep for 2-3 days/ nights. After that I struggle and will crash out. But 4-5 hours at a single stretchy, followed by 1-2 hours awake, followed by another 1-2 sleep is my norm now ( post menopausal). It’s not ideal, I’m very aware that poor sleep is now thought to be a cause of altzeimers and managing on 4 hours sleep routinely ( as per Maggie thatchers brag), is not healthy or desirable. I make a point still of early bedtime so I can get my 6-8 hours min in the 2 stretches, but still get up at 7am.
best thing is to accept night your sleep will be broken from now on and figure out what works best for you to adapt to it. Almost certainly, you’ll need to Go to bed a bit earlier and train your body to adjust to earlier bedtime. If you struggle to get back to sleep once you wake in the night (my issue and very common for women and elderly), find what works best for you. There’s all sorts of advice out there on internet- I personally use audible or podcasts with spoken voice - distracts any anxiety that starts to build about random shit, and a single voice becomes a bit of mono tonal white noise. There some recent research out there about blue noise not white noise- not looked into that yet
You will adapt to this. You may be lucky and able to restore your sleep post birth like some of posters here. But it is also better to accept it may not, and that’s relatively normal.