It takes time to excrete the arsenic.

And if you are still exposed somehow, it would still be coming out.

Interpretation of tests can vary from doctor to doctor.
A specialist might give you more information than a doctor who
is not experienced with heavy metal toxins.

This is a highly specialized problem, and we are limited here about answering it. But many of us have experience with doctors who look at test results and say "normal" when they are not.

So I would get a specialist's opinion on this issue.

Much of the data on the net comes from India, where arsenic is found in well water. Page 7 of this paper discusses nerve effects including EMG results:
http://docs.google.com/viewer?a=v&q=...24Pe-u8fE4fJ1g

Don't forget to tell your doctor about your Beau's lines. That is a significant detail that may help your diagnosis.

I would not assume bottled water is safe. Perrier had a contamination in the past! (contained benzene).
It is fairly well known in US that many "bottled waters" are just pulled from the tap, and may or may not be filtered further.