I know what you mean. Back pain has been a lifelong friend!
I now get a constant low level ache around my SI joints, just enough to stop me getting any good sleep.

The spine has two main components, the hard bits and the soft bits. Arthritis affects the hard bits causing changes to the bones.
To compensate and cope with these changes, the soft bits have to constantly reorganise and try to support the spine at all times.
This is very hard work and you will likely get a lot of pain from this area. Arthritis itself is painless, I believe.
So its causing other areas to get sore.

The best things that I have found to ease these back muscle pains are remedial massage and a magnesium supplement.
The massage will give temporary relief, and will show if you are on the right track. You may need several of them a few days apart to get on top of the problem if you are really knotted up.
The magnesium will give long term relief as it allows the muscles to relax and go back to normal.
I take the liquid form greatly diluted in water. You can get good powder forms also.
Should see a benefit in a week or so.
Best thing for sore muscles.

You should also review your mattress and pillow for proper support. If you lie on the floor, on a thin mattress say, do you have the same pain as in bed? Mattresses sag after only 3-4 years, and the back can be very sensitive to mounds and hollows as the spine tries to hold its alignment.
Pillows are notorious for upsetting the spine-too high or too low.
It takes a few days to test a new combination, so don't try for one night only.