Hello Heatrey,
I am sorry you have been going through such hoops trying to get a firm and consistent diagnosis. It does sound like PMR to me (though I am only another person with the condition not a medical professional). I, too, strongly suspected the influence of other meds bringing on PMR -- a condition I NEVER experienced before my Moderna I and II shots (no apparent after effects) but the adjuvanted quadrivalent flu shot i received seemed like one-too-many boosters for my immune system. Within 2 days of my flu shot I was wondering what was happening and it got worse and worse over the next 3 weeks until I was, as your so expertly put it, "miserable": gradually hobbling like I was 90, unable to sleep more than 3 hours because of pain, unable to bend down, use my upper arms to leverage my weight in bed, unable to rise from a kneeling or squatting position, and on and on. The prednisone has been a total life-saver for me and I will trade any side effects for the restored quality of daily life I now enjoy again. I am a bit surprised at your prednisone dosage being reduced after such a short time as that doesn't seem a standard best practice, but I don't know what other factors your doctor was considering. And I know I won't take another flu shot again regardless of the "received wisdom" saying everyone over 65 should have one annually. That is WAY too sweeping a category for all the various other conditions that exist in that huge demographic.

I am pretty new on this journey, but from all the reading I've been doing, PMR pain is classically restricted to shoulders and upper arms, and hip girdle, butt muscles, and down the legs. Its "magic bullet" is prednisone, and treatment typically begins at 15 - 20 mg with tapering beginning 1 - 3 months out, if a patient is able to tolerate it. I hope you are able to lock in a diagnosis soon and receive adequate dosages to manage the pain that virtually all PMR sufferers find intolerable until the flare wears itself out and you can taper more-or-less comfortably.

This is a difficult road and I think you have been exceptionally patient and cooperative.
I'm hoping your relief comes soon.

Laurel