There are many more surgical remedies you might venture into. Some people even have their harringtons removed. But it sounds like reduced space at L5-S1 is causing your pain. An epidural would reduce the inflammation and might help. There are microdiscectomies, laminectomies, designed to give more space to the spinal cord. Sometimes the ligament is stretched and they can remove part of the ligament. You might want to see an orthopedic surgeon for a fuller assessment (eventually). One of the more exciting new developments is the artificial disc.
Are they imaging your spine with CT?
Sometimes a vertebra will slip slightly forward over the next vertebra usually because the disc isn't patent, compressing the central canal. https://spineconnection.org/back-pain-conditions/spondylolisthesis/ It usually worsens when a person walks for say five minutes. They bend forward because that opens the space in the central canal.
Wishing you luck with this epidural.