I can't stress enough the possibility of muscle spasms. As I mentioned above several months ago I experienced debilitating back pain for @ 3 days. The doctor gave me pain pills, muscle relaxers and a week long steroid treatment and called it sciatica. The pain subsided but slowly started to come back. Before it got real bad again I focused on pinpointing exactly where the pain was radiating before the bad back pain kicked in.
For me it started in my left hip and radiated up in a fan shape. What I did was find a human muscle chart online and noticed that what I was feeling described my gluteus medius perfectly. More research said that a strained/spasming gluteus medius is often misdiagnosed as sciatica and represents as lower back pain.
I found some good specific stretches as well as learned how deep muscle massage could benefit. One suggestion was to roll on a tennis ball over the affected area. Believe it or not that has definitely helped the most. It was painful at first and I could really feel the knots. I have been doing the stretches twice a day with really good results.
Sorry for the long post but I know the feeling of experiencing back pain. Hope this helps.