Mri says i have small disc protrusion,however when having mri i had no support for back under legs so could this just be bulging because of way lying?

Unlikely positional: It is unlikely that the protrusion was from how you were laying. A normal disc does not bulge/protrude while lying down. A disc protrusion is usually caused by a breakdown of the fibers that make up the outer ring of the disc. This breakdown lets the squishy material in the center of the disc protrude beyond the borders of the vertebral bodies.