Sciatica Pain

Experiencing pain from buttocks to leg to foot (left side), pain can be debilitating and affecting my mobility (crimp walk). other days my right leg is affected as well. pins and needles and muscle cramps (calf area as well). Are these symptoms affected my sciatic nerve? also experiencing lower, middle,neck and shoulder pains. Is this also because of the pinched nerve? other symptoms include tingling sensation around face andoccasional headaches. I am taking neurontin 100 mg twice a day (does this med cause side effects like what I am experiencing above) and B complex combo. Are these symptoms pinpoint to something like multiple sclerosis or any issue on the spine.