Monthly flares

Every. Single. Month. On the 19-20th day of my cycle and lasts for a week. I suspected it was endometriosis but it isn’t. I do have endo but it was found on right side pelvis not left. It’s absolutely maddening. I feel like it’s pointless going to Dr or ER, because it always resolves itself within a week but that week is torture. Anyone have any recommendations? Diet does not seem to matter and even if not eating I have pain. Ranges from 5-8/10 so it disrupts my life and I miss work because of it.

Edit: -I had diverticulitis confirmed by CT in 2019, have had antibiotics for it twice, these flares were NOT cycle related but it’s the same pain location/sensation.

-I had laparoscopy this year that confirmed no endo around bowels

-I had colonoscopy this year that showed 12 diverticula, mostly if not all in sigmoid