What Causes Numbness And A Burning Sensation In The Leg?

I have numbness and burning sensation in my left leg while standing and moving. after a short period of time i develop a pain in the hip. I've done PT for a "pinched nerve" which was diagnosed by my doctor after looking at a xray only. They cant seem to find the source or cause of the pain/numbness. They burning senstion in my leg gets really intense. If I sit down .. it goes away pretty quickly or if i just take pressure of the leg the burning sensation goes away but not hip pain or numbness. What can this be?