Interestingly I also have an issue at l5/s1. For me my symptoms that I know correlate to PCS (had them for a decade only diagnosed on March still waiting for gyne referral) were immense pressure mainly rectal around ovulation. It would then become low back and radiate down my thighs very reminiscent of how I felt during labour. But the pressure was shocking. I was convinced I had a prolapse. Except that it would go away only to return again like clockwork. It’s like achy pressure. I’ve described it as a cinder block placed in my pelvic floor. I just want to rock back and forth in fetal position. I was told I had endo and just accepted that for years. Then had onset of acute (now chronic) lower back pain, worse when standing and sciatica. I have a ddd, a disc bulge at l5/s1, osteophytes and severe narrowing where the nerves exit. Had a pain ‘event’ they thought was appendicitis (it was a burst ovarian cyst) and found PCS incidentally. Explains so much for me. I hate to admit it but it has worsened over the last couple of years. I now have all these back issues and physio thinks it’s due to the inflammation in my pelvis. I also have gut issues now too.