Lower back pain 4 months from laminectomy, L4/5 fusion. Suggestions?

I am having, at times, severe lower back pain four months after a laminectomy and L4/5 fusion. I try to stretch, which does help, but it is sometimes hard to move without any pain. I am in PT and am looking at a trainer to help with strengthening core. Anyone have some suggestions? Anyone had this problem after surgery?