Muscle issues day 12

Day 12 on 12.5mg. Pfizer brand Zoloft tablets, I break in half. (Low dose meds always work for me) Anyway, does anyone else get muscles issues? I feel shaky and like electricity running through my muscles. I feel the fibers or something. I attempted to workout tonight, all the muscle groups were quivering; I couldn’t hold a plank. Just some body weight squats sent my legs into full on spasms, then locking up rigid, then weak and spasms again, repeat. I’m drinking electrolytes and I have a big heat pad wrapped around my thighs so I can try to walk and finish my evening. I had to hold the wall and hand rail coming down the stairs from my home gym. I’ve never had that issue before. Even dumbbell curls were barely manageable. I was shaking because the muscles weren’t contracting right. How long till this goes away? Or should I quit. I have to be able to work out, I’m doing physical therapy for my back. I can’t not work out for extended periods of time or it will get worse again.