I can definitely relate. You are describing exactly what I am going through. I keep doing internet research on muscle pain to figure out what this could be. My new Rheumatologist thinks my PMR resolved itself a long time ago and the mild muscle pain I’m feeling is withdrawals from steroids. so I am now down to 2.5 mg and working to get off steroids quickly per her direction.
I am puzzled about these new muscle pains which I did not have before PMR. Mostly shoulders and biceps. I am fit at 61 and PMR started when I was 59. I was in great physical condition. My new rheumatologist thinks I had overreaction to COVID vaccines which then resolved itself without me realizing it while I was on steroids. (Perfect labs). So frustrating that I’ve been wasting time unnecessarily on steroids for 2+ years.
I find it interesting that you are describing something similar. I was hoping these pains would go away over time after stopping the steroids but it sounds like in your case it has not happened yet.
I have been looking into fibromyalgia (but symptoms don’t match) and also getting shoulder X-ray next week. But I’m am doubtful anything will show up. have you looked into other conditions?