Nipples are so sore but not my breast itself.

My nipples been super sore for the last week. I have had tender breast and nipples at the same time often especially around AF is due. This time around is different, I have sore nipples only. My period is due on the 19. I could possibly be pregnant but I'm not really thinking that. I'm just wondering if it could something else besides pregnancy and has anyone else experienced this?