Muscle pain during treatment?

I've had 4 sessions of TMS now. (The first didn't really count because the technician mapping was slightly off.) Starting a day or two ago I woke up with soreness in my back on the left side and hips, mostly on the right side and going down my right leg like I did a workout or something. Maybe it's unrelated but I haven't done anything out of the ordinary that would cause soreness in my muscles. I feel like it's getting worse. I asked the facility and they said they hadn't experienced anyone getting paid like that from treatment before. Has anyone else experienced this?