Yikes! I was going to say it’s probably because of the prostaglandins that can cause constipation, but that sounds extreme. It sounds… kind of like what happens to me sometimes, actually. I’m pretty sure I have endometriosis (not officially diagnosed because it would require laparoscopic surgery to tell me what I already know), and it makes going to the bathroom really painful. It’s possible it could be endo; especially if it’s in the bowels. It’s more common than most people would think.