I pulled this from a side effects sight:
An allergic reaction is a possible Zoloft side effect. Stop taking Zoloft and contact your doctor immediately or seek emergency medical treatment if you experience difficulty breathing, closing of the throat, swelling of the lips, face, or tongue, hives, a fast or irregular heartbeat, jaw, neck or back muscle spasms, shuffling walk, slow or difficult speech, persistent fine tremor or inability to sit still, fever or severe skin rash. Contact your doctor immediately if you experience yellowing of the skin or eyes.
You might want ot call your Doctor. I had a similar reaction to Bentyl, but it was my jaw. It started rapidly spasming and I couldn't stop it. I went ot ER and they knew what it was and gave me an injection of epipeniphrene I think and it immediately stopped!