I have been diagnosed with Forestiers Disease or DISH (diffuse idiopathic skeletal hyperostosis).The symptoms are chronic back pain and stiffness caused by the calcification of the ligaments.It is associated with increased BMI and more likely to occur in type 2 diabetics.It is everpresent at low levels,but regularly lays you flat for several days or weeks.
Some people think it is yet another auto immune condition and it can be associated with arthritis.Doctors are rubbish at diagnosing it and in my case it took an MRI and a consultant to get a definitive answer.
I controlled it with nurofen and chiropractic manipulation for years,however when I read your post I suddenly realised that I had not had an attack for over six months,which is unprecedented.This coincides with me undertaking the Newcastle Diet last year,during which I lost 10kgs,and attained a normal BMI.My blood sugars are also coming back in the normal range even though I am off medication.
Your back pain could be yet another side effect of diabetes.