Yes, I've used those. The ones that I've used are called a TENS unit. We store toxins in our muscles, so as PeteZa said, you will need to detox, and maybe more than usual when that is used.
As far as doing more harm than good, that's something that you will have to determine. If you can't seem to detox enough to keep your headaches and any other symptoms under control, then you will likely need to either limit the amount of time you use it, or stop using it all together.
Best of luck!
Herb only treatment for Lyme & Bart ended 12/11 - no active symptoms for 2 yrs -Herb only treatment for Babesia ended 12/12www.healingwell.com/community/default.aspx?f=30&m=2977364
Had Lyme, Bart, Babs, RMSF, Ehrlichia, Myco, Anaplasmosis, EBV
New Lyme case 8/2014 - Healed 1/31/15 - unknowingly had Asymptomatic Babs and Asymptomatic Bart, being treated now though (2/2016)