[sammyg2]

Re-re-post, but might be relevant:

This is something I posted years ago:

That got me through many years of back pain without missing a day's work.
I got to a point where I could ignore almost all pain at will, I got to where I enjoyed some pain just so I could prove I controlled it as strange as that sounds.

I have a scar from L5 to S1 and suffered from back problems for many years. It was no big deal to go get cortizone injections directly into the back every other month or so.
But I haven't had ANY back problems in the past 5 years.
What did I do? I learned how to sleep right.

Take a really good look at your sleep posture.
There's a good chance based on your description that you end up on your side but your shoulders and hips are not parrallel.
I'm also betting that your hips tilt over more than your shoulders, which puts a slight twist in your spine. A twist that the muscles must contract a little to control and contain.
That means the muscles do not get a chance to relax, so they get fatigued, and weak.
If that isn't the case then please disregard.

But if that is indeed the case you need to train yourself NOT to sleep in that position. That is important.
Problem is, that happens when you're sleeping so it's hard to correct that bad habit.
Pillows help, especially one between the knees.
I've found that a firm mattress is not necessarily a good mattress, in that if it's too firm it encourages bad sleep posture.
It'll take time but when I finally trained myself to eliminate bad sleep posture which took the strain off of the muscles in my lower back and allowed them to rest, my back problems went away completely.