PMR and fatigue

The symptoms of PMR started 4 months ago however I have just been diagnosed with PMR recently. The confusion in the diagnosis has been due to the fact along with the pain and stiffness I have issues with fatigue, brain fog and cognitive issues. I started on 15 mg of prednisone and have gone up and down based on flare up’s and am on 9mg at the moment and feel little or no pain and stiffness. Previous to the onset I was fit and well and always on the go. Now I have to plan everyday around the 2-3 hour window I have before it’s time for a sleep. After my sleep, I may have another 2 hour window. The symptoms and how I have to deal with are very much like chronic fatigue.
I see conversation around the pain and how this can lead to fatigue however I am pretty much pain free at the moment. The doctor has said that this level of fatigue and brain fog is not uncommon with PMR and is probably caused by a sensitivity to prednisone. Any thoughts?