The "cortisol is raised by stress" is a myth unless you are morbidly afraid of needles and screaming at the time of the test, just told about a death or someone tried to kille you during the test... Some docs even put in picc lines to preven the stress of a needle for long testing (yeah like that is not stressful!) but a friend's mom who was deathly afraid of needles and did almost pass out w the draw... Had a normal cortisol.
It may not have been flagged as cortisol needs to be tested at certain times to be diagnostic, but it peaks at 8am and should fall, not rise after. So yes, a trip to the endo is in order.
Sadly, most endocrinologists are pretty clueless when it comes to Cushing's disease so it pays to do some research on how to test (8 am fasting) and if the doc immediately wants to doc dex test, walk and find another (it means the doc has zero clue, and most people suppress as it is a great test for source, not exclusion). If they want one test and wait 6 months to see you... Ugh... Another bad sign.
Once you get imaging and enough proof, move on to a pituitary center. Get copies of everything.
Good luck. I know in my case I had to see over 10 regular endos and probably even more neuro-endos as I had cyclical Cushing's and most say hormones don't cycle. Period. Hah!