I had that a few years back & found that I was allergic to Opium based painkillers. With PD the contracting & rigid muscles in the back conspire to compress the spine!
After a MRI scan it was recommended I should have surgery but I decided first to visit a Sports injury Physiotherapist and requested that he stretched my spine after a massage and to my relief the problem eased.
I then designed floor exercises based on the Physiotherapists advice to help stop a return of the problem…
That was at least three plus years ago and I have not looked back.
My exercises are described here [https://sites.google.com/site/beauxreflets/keep-fit]
Kind regards and hope you solve your problem with the help of Physiotherapy too.
My apology for not following the Forum for such a long time.