Bulge at l5s1 when i walk or stand for more than 15 min the skin on the l side of my back goes numb- why?

Dermatome affected : You didn't mention exactly which part of the skin on your back went numb, but i'm assuming it's the same area that you have a disc bulge? Disc bulges by themselves are usually not problematic. However, if you have some type of sensory nerve, or irritation to the cutaneous nerves on the skin, you may feel as if it has less sensation. You may want to go back to the physician who, last saw you for this: your orthopedic surgeon, or physiatrist, and get more information as to treatment planning. Hopefully they'll have options available for you to consider that are nonsurgical.

See your DR!!: Radiculopathy is a reference to pressure on a nerve, often by a disc as the nerve leads out of the spine. Sounds like you are sick. You should go for help.