I'm truly sorry this is happening to you. You are very lucky you have a Rheumatologist that recognized your secondary AI. My symptoms were very similar to yours. It started at about 4 mg prednisone per day. Vertigo, nausea and periodic elevated heart rate. But my rheumatologist never supported a diagnosis of secondary AI. He would not refer me to an endocrinologist. My attempts to do that weren't met with support from the Healthcare system. I finally got in to one and he was, to be frank, an Ahole. He said I didn't have it without even attempting any type of testing. It was very disheartening to know I was going to have to go it alone. My rheumatologist's one saving grace is that he's allowed me to taper prednisone very slowly. I'm currently at 0.75 mg per day and plan to go to 0.5 mg on Monday and hopefully be off the drug by mid to late September, God willing. My PMR pain is around a 2 or 3 on a 10 scale, mostly in the am before my prednisone "fix" and late at night. I will have been taking prednisone for around 650 days.....

Stay the course, stay positive and try to move as much as possible, given your level of pain. Swimming, walking, pilates and stretching have kept me sane during this ordeal.