Periods aren’t usually a pleasant experience to begin with, but certain signs and symptoms may point to a more serious condition called endometriosis. This condition has to do with the lining of the uterus, which thickens with blood every month before your period. However, when this special lining grows outside the uterus in other areas of your abdomen, it can cause extreme pain and discomfort. Dr. Amber Bradshaw-Whitear of Ogden Clinic points out that this lining may grow on any structure in the abdomen, although it’s usually contained to the pelvic area. While symptoms may begin as highly painful periods, they usually develop to a more consistent pain as endometriosis worsens. Other symptoms include pain during intercourse and problems with infertility.