Testing for heavy metal toxicity

I had an 8hr 250mg DMPS challenge last year which showed no significant amounts of heavy metals.

Funny thing is, during the DMPS infusion I had a lot of neurological problems. Difficulty stringing a sentence together, stuttering, general unwellness and had metallic taste in my mouth for the rest of the day.

For days afterwards I had increased sensitivity to light, sound, and worse overstimulation.

I was expecting based on this that surely the test would show that I had heavy metal toxicity.

How reliable is a DMPS challenge? Is there a better way to assess heavy metal toxicity?

I don't want to go through chelation unless it is absolutely necessary as I am *EXTREMELY* sick.

Thanks.