I had (...long story) a Spinal Cord Stimulator for 9 months and never had any side effects. My leg jerks (which is my effected area) sometimes even my whole body but it's for a split second only.
I would think that that is something that needs to be addressed........like NOW! You're doctor doesn't seem to concerned. Take a video of a seizure and show it to em. Maybe he'll care a little more!
What's worse...not having the SCS and dealing with the pain or having it and dealing with seizures. Sometimes the things that are supposed to help make things worse. Sorry you have to deal with that.
Good to luck to you. Hope you find some relief soon

Heather