Waking up to Sphincter contractions

I think the pain started in my 20’s or 30’s. I am now in my 50’s. I was not diagnosed with endometriosis until my 40’s. I never put two and two together that my endometriosis had anything to do with this painful and annoying experience of waking up in the middle of the night with my anus muscles so tight it was excruciating. I found no relief except time, about 20 minutes after waking it released and I could go back to sleep. My identical twin sister said she found it was about a week before her period would start. Menopause has lessened the rate of occurrence, but it still happens occasionally. It doesn’t happen during sex or orgasm, pretty much mostly at night for me. My twin doesn’t profess to have endometriosis, she also experiences these sleep contractions.