I sat on a plastic chair in my work kitchen for about 20 minutes having a sandwich and when I got up I had low back pain, spasms in my low back on the belt line, and it hurt for 2 days. My doctor is treating me for SI joint problems so I've been wearing a SI compression belt for 4 weeks so far. I have also had an xray of my coccyx and looks pretty normal. I sit on a cushion at my desk or I would not be able to have a job. I don't know if a disc could cause this problem or not. Please let me know if anyone is experiencing similar problems.