Numbness in a Leg

Well, now my back pain has progressed a tiny bit. I still need painkillers, but the worst part is that in the last 3 days, I have numbness in my left leg, from my hip to my knee. Usually just above my knee. I thought it was a circulation problem at first and then realized it's got to be something else. So I have to go to ER again, because they said to go back if I had numbness or tingling. This sucks.