11 days ago I missed a step while walking down the stairs and landed on my left lower back. Initially it felt like a bad bruise so I rested and iced it. Although it felt like a bruise no physical sign of a bruise has ever appeared. I had to move rather gingerly to make sure the pain didn't get worse. About a day or so after that I started getting sharp shooting pains about 6 inches directly below where I hit my back. These pains did not spread anywhere else except for the one spot below my actual injury. These sharp pains were bad enough to take my breath away and caused tears to well. I did go to the doctor and she briefly checked me over and determined that I had injured a muscle which was spasming and causing the pain, which she prescribed a muscle relaxant for. Even with the muscle relaxant and Aleve these sharp pains would not subside. 11 days later my actual injury feels almost completely gone, but I still get the occasional sharp pain, although it does not hurt as much or last as long (only about 5-10 seconds now). These pains usually happen while trying to put on shoes, getting in and out of cars, or sometimes with the slightest of movements. Does this seem like more than just a muscle spasm? And if so what might it be and how serious?