What Causes Tingling Sensation In Leg?

4 months ago i was doing some heavy lifting. I noticed a week later that my lower back started to hurt and I was starting to feel tingling in my left leg. The tingling seems to get worse whenever I sit now. I have had an EMG and an MRI and nothing was found. Also 12 yrs ago I had herniated discs in the upper part of my neck. I had surgery where they repaired the disc with fusion. Could these symptoms now be related to that?