Greetings, sorry about your concern.   When you have pain, spasm will be present, spasm is nothing but increased contracted state of muscle which has failed to relax after an activity. In your case electric stimulation is a bad idea.   Electric stimulation only causes more contraction to muscles which is already in a contracted state.  If you can identify which muscle is in contracted state and leaving that muscle and stimulating the muscles which is inactive near site of injury is a better approach and will be good if ems is applied.  if you can find a therapist with this kind of approach then you are in a better position to cure back pain.

Electrical Muscle Stimulation (EMS), is non-addictive. Exercises are possible after spasm reduces. Spasm comes due to muscle injury. It comes only if you do excess, over activities, and strains your body with more than normal limits. Hot water bags can be applied 30-45 minutes, it will reduce your spasm; IF without any big problems inside.