I also have really bad cramps from my stomach and pelvic area. also, my breasts have never been this sensitive before. what is happening?

Pelvic and abdominal pain has several possible causes, some of which are serious. Assuming you are sexually active, pelvic inflammatory disease (PID, Fallopian tube infection) is a good possibility, generally caused by gonorrhea or chlamydia; and is especially likely if you also have vaginal discharge or fever. Any new or unexplained pain like this needs prompt medical evaluation. Good luck.