Ribs hurt. hard to breathe.?

Ok so i havent done anything strenuous lately, especially not to be affecting my ribs. but it is right over the middle of my rib cage and a little bit beneath. it does hurt to breath, mostly inhaling. it does not affect my back but when i turn to either side it affects my stomach slightly. could these also be really bad cramps for menstruation?? it was a sudden burst of pain and if i can recall it hasnt been the first time this has happened.