Hey, Hopeless. I think your best bet is to find a very good endocrinologist and let them know your symptoms. They have tests they can do to determine if any levels are off, such as ACTH.
I like Medscape, for thorough descriptions of conditions.
http://emedicine.medscape.com/article/116467-clinical
Diet is so important, even while on Pred. There are books devoted to living well while taking it.
Yes, of course, adrenal insufficiency effects can vary and to different degrees.
You probably should talk to an endo about possibly being pre-diabetic. Dietary changes can help with that, too.
Since so many of us with an autoimmune disease have more than one, I think your questions are very appropriate to the conversation!
I hope you will find an endo to evaluate your symptoms.
Annie