I had the same thing from DS and then a hematoma (sp?) developed after DD1's c-section. I still have it in my back, but its not as pronounced 2.5 years later. I think they are a common side effect, my chiro sometimes works on my back and tries to loosen it all up and it bloody hurts, but I remember for about 18 months after my section with DS that I couldn't lie on my back on a hard floor or sit against a wall because it would hurt too much in that area.