Your doctor should have done an MRI instead of a cat scan. It is much better for soft tissue injuries. Additionally, I fell and had horrible back pain which arose from the fact that I had twisted my pelvis, this could also be happening from lifting. When the pelvis twists, it twists the back and the nerves and it can be very painful. It can also twist the periformus muscle in the base of the buttock. The sciatic nerve travels through this muscle or under it and that twisting can entrap the nerve causing buttock, lower back, and leg pain or burning.