If you were almost to the second trimester then that really does sound low. You should get your ACTH tested if you have not yet. Since you have skin darkening, then your ACTH is probably high (indicating primary adrenal insufficiency ... an autoimmune condition sometimes associated with Hashimoto's.)
The 24hr urine test is not that good at detecting LOW cortisol. It is normally used to detect HIGHcortisol. So it doesn't necessarily mean anything if that comes back perfectly fine.
Saliva testing is good. Not sure if I trust those home kits you mail in yourself. But my endo told me that that the "real" saliva tests that doctors/hospitals use are very good.
Good luck.... an definitely find a new endo if you don't like or trust your current one!