In my two pregnancies i experienced back labor and it was mostly just my lower back but really painful... i felt a burning sensation like the pelvis opening...lol the only thing that kind of made it to calm a little was walking and a massage on my lower back..
For me it was a constant, and I mean constant severe low back pain, wrapping around my low hips and into my legs.
Think of sitting for hours or the pain after camping... For me it went from tail bone and grew going up to my ribs area, it was hot and horrible... That's only way I can describe it.