Do a lot of people suffer from endometriosis? how common is this?

Its fairly common: Always hard to tell because you need a laparoscopy to confirm the diagnosis, and people with pain get a lot more laparoscopies than people without. That said, when I do laparoscopy with people with pain, a huge percentage of them have endometriosis, well over 50%. There is selection bias here to be sure, but I think we can safely say that its not an uncommon disease.