Okay so my period is usually a 26 day cycle and ever since May it has been 1 day late or one day early. I know i can't possibly be pregnant because the last time i had intercourse was in February and me and my partner used a condom. I have had my period for 6 years now i would say it's still regular i am 16 years old. Also my period has been lighter than usual ever since my period has been a day late or a day early. I don't believe this is pregnancy what could it be ?