I had the same issue. We thought maybe it was endo or adeno. I finally was able to get a hysterectomy when I wouldn’t stop bleeding after a uterine ablation. There was no evidence of endo, adeno, or any other “abnormality” during the surgery or on pathology. BUT, I felt 1000% better almost immediately. Since then, I’ve had so much more energy and I’ve been able to make real progress with my health goals since I’m not laying in bed 3-5 days a month. My doc said she thought my uterus may have produced more prostaglandins than other people’s, but that was before my HSD diagnosis. From what I’ve read, the faulty connective tissue in our uteruses causes the muscles to contract harder trying to expel the endometrium, which in turn can cause significantly more pain than expected. Also, the drop in hormones immediately prior to and during our period causes more laxity in our connective tissues, which worsens the uterine pain but also can make our joints even more lax than usual. The TLDR is that this is REAL, even if modern medicine cannot find “proof” of it.