Had my period but....

Heather • Im just me, mom, stepmom,
Ok so i was a day late on my period. It came but i usually go for at least 5-6 days, it only lasted 4 this time, i had sex with my fiance before i stated n havent had sex sense then, but my breast are really sore n idk? I took 2 pg tests before i had my period n they said i wasnt...so could they be wrong?