It does sound like either hyperkalemic periodic paralysis or paramyotonia congenita. Both are caused by mutations in the sodium ion channel in the gene SCN4A. You can get DNA testing at Fullerton Genetics Lab or Athena Diagnostics. I would ask for a referral to a geneticist who can help set up the testing.
Also if you haven't seen this site, it has lots of information on HyperKPP and PMC: