What Causes Persistent Lower Back Pain?

Yea for the past 12 days I've had lower back pain, it started with sharp sudden pain all over my lower back but it got better while I walked to work, before yesterday I felt no pain then I did 5 minutes of punching excersice and it came back a bit, then yesterday morning I felt fine so I went to work and when I got home it was bothering again, I'm afraid it could be a herniated disk or some sort of disk problem.