You should try drugs for neuropathic pain if you have not already: amitriptyline, gabapentin, duloxetine, and many others.
It's been a bad 5 to 10 years. My opinion is that "pain syndrome" was almost certainly not my problem. My pains were all skeletal/joint pains, except for pains that would suddenly appear in my left hand or right calf, even when doing nothing. Those latter two I could explain as being neuropathic, but after being in so much pain from my back, coccyx, hips and shoulder, I think my pain registration system was out of whack. And I wouldn't be surprised to discover that all the different "pain killers" I was taking were in fact contributing to further problems.
Currently I am just on morphine, but must tie myself to the bed at night to stop myself turning over in my sleep. If I lie on my sides, the pain will build (even through morphine) until it wakes me up. By that stage turning on my back will not reduce the pain and I cannot get back to sleep. Taking a sulphur supplement (NAC, or MSM) seems to be as effective as morphine (neither alone or together is really satisfactory though).
What has been so appalling in my case, has been the difficult of getting doctors to look at the individual problems properly in early stages (so a dearth of scans/treatments), until it got to the point where they were saying "you have pain syndrome". Most of the treatments that have had any success are those that I have insisted they do even when they have said they won't work. Some major treatments I have had to insist they don't do (cutting nerves??).
I'm finally getting a scan this week on my hips, after asking for this for almost 2 years. Hopefully it will show what I expect it to show, and they can treat it with steroids.