I've had to learn to get by on a lot less since my back went. I can't sit for any length of time, nor can I stand for any length of time, and you have guessed, I haven't been able to lie down for any length of time. Until I moved to Australia I would sit in my OAPs chair as I called it (a riser recliner - the sort you see in OAP homes that can lie flat or throw assist the occupant with standing. That allowed me a whole load of different options, but we couldn't bring it to Australia for a number of reasons not least of all I still needed it whilst it would have been in transit.
So now I try to get by. Sleep wise I go to be around 9-9:30pm and wake at intervals during the night - usually 2 or 3 times, though just recently the Drs here have changed some of my meds (over to synthetic morphine and increased the dosage) which has meant that I have, for the first time in 2 1/2 years actually slept through to the alarm at 5:30am (it was 6am until daylight saving ended here in Australia at the weekend, but the chooks need feeding and letting out and the sunrises at 6am currently so...). I don't get anywhere near like the 8hrs you're meant to get and periodically collapse as I did on Saturday (and I mean literally). My hubby put me to bed around 11am and I didn't wake (except for my medication alarms) until 6pm, got up, fed the chooks, put them to bed and then ate as well, then went back to sleep until 10pm when hubby woke me for more meds, and slept through til 6am.... usually I am a touch better than that and pick up on the warning signs but missed them this time.
I would love to be able to curl up on my side again and get some sleep, but my ribs (I broke 11 in a fall back in November) and my back (November 2014) prevent me from doing so! I can't even sleep on my own side of the bed at the moment because I still can't roll into the sitting position (anyone with a bad back who has had either surgery or physio will know the 'thing' I'm referring to) because my left ribs haven't healed properly get!