It sounds like your medication is not on the correct dose... ask for another blood test to check. It can take years to get it right, but once it is, you shouldnt have those problems. Ive recently been looking into diet to treat addisons, and there is a bit of info out there on the internet. Things I remember is licorice (has an enzyme that acts similar to cortisol i think), fish, tomatos, citrus, salt. And to avoid things high in potassium - bananas, oranges, salt replacements. These are just complementary to medication however, and can't completely replace it. I tried researching wether following a diet of only things on the recommended list would allow me to at least decrease my dose (im concerned about the long term effects of being on steroids) but i couldnt really find a conclusive answer and havent properly tried it myself. But my advise is to google addisonian diet and see what comes up!
Let me know if it works for you. Best of luck!