Get into your dr for a check up right away, you need this follow up appt on the record. especially if anything gets worse.

Often whiplash will take time before it really hits you.
And with the complication of the cervical stimulator acting up that needs to be documented.
Esp if it was working fine before the accident and not right afterward..

The person at fault (their ins company ) will most likely require proof (doctors reports/documentation) if it starts to get expensive..