Gem, the adrenals can be messed up if one is mercury intoxicated, same goes for thyroid (as others have intimated, thyroid may be a significant part of your issues, in spite of negative tests, since thyroid can relate to Depression and to weight issues). Furthermore, mercury messes with the entire endocrine system, so, in addition to the adrenals and thyroid, consider its effects upon the sexua| glands. Mercury is well-known to mess with women's monthly cycle, for example.
Do you have recurrent infections? (e.g. bronchitis, warts, candida, nail fungus, parasites that won't clear)
Have you ever have dental amalgams?
Do you recall when your symptoms began? Had you just had dental work or just gone abroad?
I'm new on these forums but I've been having a conversation with Sal, the past couple of days, and you might find the thread at least partly relevant:
Incidentally, I'm mercury-intoxicated and I've had sinus issues every day of my life since my school days, more than 25 years ago. I suspect this relates to childhood vaccinations containing thimerosal (I've never had dental amalgams). Mercury dramatically suppresses the immune system.