I had the same problem about 10years ago after I was doing a lot of riding. It got so bad that I could not sit for more then 10 min without beign in significant pain. I went to the Dr. he put me on muscle relxants and gave me pain medication which did absolutely nothing. I had a one of my co-workers... a PT ( I am an OT)help me a bit. What I figured out was that my hamstrings were and still are very tight which pulls on the lower back and my core strenghth was very weak. I focused on a lot of stretching, did yoga and back exercises which helped. If I don't stay on top of it, it flairs up again. Good luck. Back pain is no fun