The pressure on discs in back lower lumbar are about 1/2 body weight when standing. When sitting, it is close to double body weight in general. If you have a protruding disc or torn disc, the increased pressure could make the disc bulge and cause irritation. There are multiple treatments for this type of pain. Also, sacroiliac joint pain commonly causes low back pain. Good physical exam, history and dx studies x-ray and/or mri by pain mgmt physician could result in better dx and treatment.