Your symptoms sound like adrenal insufficiency to me. Adrenal insufficiency doesn't need to be caused by Prednisone. There are underlying autoimmune conditions that attack the adrenals or thyroid and other things which cause havoc on your endocrine system. These conditions can be insidious and symptoms wax and wane depending on the day.

There is no "normal level of cortisol" there is only a "normal range" but that range is variable and depends on the circumstances.

Google artificial intelligence agrees:
This statement is accurate; while a "normal range" for cortisol exists, it is not a fixed number, and can fluctuate depending on factors like time of day, stress levels, and individual variations, meaning there is no single "normal level" of cortisol.
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"I’m not one to want to take medication and I don’t want to just mask symptoms. I want to get to the root of the problem and find a real solution."
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I don't think modern medicine works this way. I'm a nurse too. I would sometimes feel guilty giving patients so many pills because I felt like I was contributing to their problem.

You aren't psychomatic but it is easy to be labeled as such. I was labeled as "noncompliant" by my very first rheumatologist. My very first primary care doctor said he thought I was a "crazy person" who wanted prednisone but later apologized for thinking that way.