Endo - there are two theories/types, retro bleeding at AF into your abdo and/or born with endometrium lining outside your uterus which "bleeds" at AF. So the endo wouldn't be getting worse as your progesterone levels aren't low enough to cause the slough of the blood. However, if you have endo in forms of adhesions etc in your abdo then these could be aggrevated by the stretching of the uterus. Depends on the location of the endo "spider webs"/ or if you have chocolate cyst./ove.