Sandra,
Dallas is right about the magnesium. It is the one thing (and believe me, I have tried it all) that I can say for sure has made a tremendous difference for me. Some things to remember:

-mercury blocks magnesium
-different forms: citrate is good for people who need help with BMs, but it does draw water into the bowels, therefore can cause dirrhea if you are not needing help in that area. Oxide is the cheapest form, but not absorbable. I found a liquid that I like-www.mgwater.com
-DON'T take a calcium supplement. When you are mg deficient-and you are with mercury posioning-you will get even more so if you take calcium because it needs mg to process the calcium and will pull mg from your bones and muscles to do so. I became deathly ill (literally) when my Dr. put me on calcium supplements.
-the mainstream thought that you need twice as much cal. as mg is based on the amount in your bones and doesn't take into account the mg in the other parts of the body.
-blood serum test are not indicative of the mg in the body. You must have a red blood cell test of ionized test done.
-you almost can't get too much mg as you will pee out any excess. The only way that I found is if you have kidney problems.

As far as the thyroid test, I also had all the symptoms with good test. Mercury messes up the process of the conversion of the T4 to T3. This won't show up on the test.