What Causes Sore Nipples With Irregular Menstruation?

i have been having sore nipples for over a week now but not breast tenderness. i dont expect to have a period unitl about 25 more days. im verry irregual with my periods. i try to keep track to etimated when i will be getting a period. i dont cycle every 28 days. when i get my period i dont cramp on suffer like other women. which is why im concerned about my nipples been so sore they hurt even with my bra sometimes. im also having a lil sharp pain in my lower abdomen. any ideas why im feeling this way???