I think i might have spondylolysis, how to tell for sure?

Spondy: Some can be seen on plain xray but ct scan is best test with sagittal reconstructions ortho spine or general ortho can doevsluation

Imaging: First see a doctor to see if it's even necessary to check for one. If it is many imaging methods can pick it up. Best is ct scan, but plain x-rays can pick it up well. Mri can show it also but less well.