I injured my low back 10 years ago while on a rowing machine. I've had an L5-S1 fusion, to no avail. I can't sit w/o pain, only lying on my stomach.

Impossible 2 answer- -here. You need 2 return 2 your surgeon, or if not possible, see a fellowship trained spine surgeon. There are many causes new & old. Failed fusion, adjacent disk disease & more. .