Why such a bland diet?
If your body is craving salt - give in and have the salt. Try it and see if you feel better. Your body is trying to tell you something. It is a sign. Have you obtained any copies of your past labs - any low sodium testing? If you don't have appetite - get salt tablets or drink something salty or just salt your food. I use sea salt as it tastes better.
Doctors tend not to see anything. Addison's hyperpigmentation tends to be more brown though and not yellow - so I hope they have checked out your liver and gall bladder.
You need a decent endocrinologist and yes, they are hard to find.
Suggest finding an integrative doctor who will test thyroid - FT3, FT4, RT3, check cortisol levels, and order a brain and pituitary scan with contrast. Other tests will be determined by the results of those tests.
I think you may need to check out several things, due to the Symptoms mentioned, Do you have a home blood pressure monitor, if so a home test exists for adrenal insfficiency, let me know if you have the BP Monitor, If not you can do the other home test, Have a relative or friend with you and a flashlight, go into a darkened room, sit for about fifteen minutes in the dark so your pupils constrict, then have the whoever is with you, shine and hold the light into an eye, and watch the pupil of your eye, If the pupil dialates (Enlarges) and stays enlarged, you don't have an Adrenal Issue, if the pupil dialates and constricts back and forth, then that would indicate Addisons Disease or Adrenal Insufficiency. If you have the BP monitor, attach the cuff to your upper arm, have a pencil and paper with you, lie down on the bed and rest for 20 minutes, take your BP while prone, stay lying down and note the BP on the paper, Then stand up and take your BP, if the result is the same or lower than the prone position, this would indicate an Adrenal Issue, Normal would be if your BP increases by 10-20 on the monitor. Has your MD taken any lab tests for thyroid ie: Free T3, Free T4 ?
If so post them here with the Reference ranges provided for each. Let me know what your outcome is on the home adrenal tests. Best Regards FTB4