Mercury toxicity has 2 main sources: seafood and amalgan fillings (dental). Few doctors ever consider testing for it. I believe there is a battery of testing (blood, urine, hair) because the organic (seafood) and inorganic (amalgams) forms of mercury are processed and stored in the body differently.

I am going to include a link to an article by Dr. Mark Hyman about it:
Mercury: Get This Heavy-Metal Poison Out of Your Body - Dr. Mark Hyman
Dr Hyman is well respected in the functional and alternative medicine arena. Some people are very close minded when they hear the words "alternative medicine" - if that applies to you, just try to look past that and read the info because it is based in real science and "real" medicine. There is a lot of information out there on mercury toxicity if you're willing to google. And educate yourself.

Take it for what it's worth, but it seems you have arrived in a place were reliance on the VA for your wellness is proving inadequate. That's not meant as a VA bashing. Rather, you are at this critical juncture that you can either go with the VA flow (passive participation) or become empowered by educating yourself and become your own health advocate.

As a side note, there are 2 threads in the Depression forum here on PC - "Mad in America" and "Prevention" - that has engaged a lot of he PC community that kind of centers on conventional medicine/mental health industry and how it may not (is not) be serving patients very well. I mention it not to embroil you in a debate on the topic - rather, to let you know there are other approaches and resources that merit a good degree of consideration. You might find some ideas therein that would be useful to you.