I feel pain in my left leg, which starts from left buttock and runs through left side of the leg. Pain increases when I drive or sit for a long time say 4-6 hours. If I'm walking then I don't feel any pain. I have consulted 6 different doctors, for the last 6 years, but no solution for this pain. Some say it's pciatic others say it's nerve blockage, MRI report shows two points of lower back bone as black, whereas normal portion shows all back bone as white.