Welcome, Dalby. The symptoms of Lyme disease can mimic symptoms of PMR. I'm not a doctor, but my understanding is that prednisone (corticosteroids) are contraindicated for Lyme disease and can lead to worse outcomes.
- Steroid use linked to worse outcomes in Lyme disease-associated facial paralysis https://www.sciencedaily.com/releases/2016/09/160906182119.htm

The fact that prednisone is helping and your feeling results seems to substantiate the PMR diagnosis. Did you notice any improvement after taking the antibiotic Doxycycline for 30 days?