My daughter was on Pred for many, many months and had all of the same symptoms you have. When she was totally off for 2 weeks, her Endocrinologist ran some tests to make sure her adrenal glands were working. One was an 8 am cortisol test. Thankfully her adrenal glands did recover, but she still had the pain and insomnia. She ended up taking Trazadone for sleeping.
take lots of B vitamins for your adrenal glands.