I just noticed this message when checking out the board as have not been on for a while for the holidays.
Kidney stone pain can cause pain in the back & the pain can drop you to your knees. The pain in bladder can be as the stone is moving from kidney through ureter into bladder and then out of the body. If you think you might have stones, try straining your urine so you can see if it passes. Drinks lots of water. Real lemonade is suppose to be good for stones. Stay away from too much tea, coffee, and cola drinks.
I have also had nerve pain as well unrelated to kidney stones. Everyone is different but for me the nerve pain went down the left back side of my leg/foot. This was due to the L5/S1 being herniated. Sometimes the pain felt like my leg was on fire and it also caused numbness.
Hopefully you got the results of the CT scan by now & know what is wrong.
Here's to hoping you are no longer in pain