Have severe pain in lower extrem x 2 mths. Dr switched me to atorvastin from pravastatin. Could this b side effect or fibromyalgia?

Yes. A new symptom that occurs after a medication change certainly points to a possible cause-effect relationship. Speak to your doctor immediately as statin drugs often cause muscle pains (myalgia) and /or muscle inflammation (myositis).
Probably statin! Fibromyalgia causes pain below the knee. Statins can affect thigh muscles and lower leg muscles. You should tell your doctor first. A CPK and myoglobin would be most revealing. Generic Lipitor (atorvastatin) is much stronger than pravastatin, and patients can have problems with one statin and not another. Again. Discuss the issue with your physician, the more quickly, the better!