Cramping a week before period??

According to my calendar i have about a week until my next period. Today I've been cramping like crazy. My boyfriend and I have had sex but I am on the pill, he wears a condom, AND he pulls out. So.... i doubt it's pregnancy, right? Could it just be ovulation or pms? (Also more tmi... i do suffer from ibs so could it possibly just be more intense cramping because of that?)