Ok, I slept crappy with huge melonbelly pulling all over the place, and pillows between knees etc not helping at all, until my also pregnant friend put me on to one of those yellow waffle things you put on top of the mattress (under the sheet). Looks like yellow foam egg carton or similar, and is usually quite cheap. She folds hers twice, I fold mine once so I am buffered and still have enough area to roll around. Cradles your belly, so it doesn't pull on your back and hips. (also protects mattress in case water breaks, which is nice).
The other two things that really help me are a)kick dh out of bed so have enough space and do not need to worry about waking hard-working bread earner when ungracefully trying to move, and b)those nights where I'm just in miserable pain for something or other, take a tylenol. I do that very rarely, but when I do, I sleep.
Just wanted to share. Hope it helps somebody.