I fell about 3 days ago pretty hard on my butt. Now my back hurts on the lower right side, just under my rib cage. It is a constant pain.:( There is no swelling. Just a lot of pain. My ribs are fine. But just under when I touch there is a lot of pain, and pain deep inside.

The best thing is to go to see a doctor and tell him or her what you have. It's difficult to say what you have from the net. How did you fall exactly?

It could be your muscles due to the fall. Do you feel it all the time? Or on specific occasions? Try consulting a doc, he'll know what to do.