Leg pain is one of my main indications that my period is about to come down. But this has been the norm for me for about 12 years. I've never been diagnosed with sciatic nerve but my aunt said that is exactly what it feels (she had it during pregnancy and I've described my pain to her). So for me, its common. But if you JUST start experiencing this, I guess it isn't all that common for your life style. You can try going to the doctors, but they have never been able to help me
so good luck!