Spondylolisthesis?

i have been diagnosed with spondylolisthesis in 1999, and have hoped over the years it would get better, they say it was congenital but a car accident i was in aggravated it- my back pain is unberable in my line of work (nursing) is there any suggestions to help relieve the pain (besides strengthening abs tosupport my back) bc the last thing i want is an operation for a back fusion - please any suggestions would be greatly appreciated THANKS!