hi, im 26yrs old and and i think i might miss my period this month because last month when i had sex i took an

an ipill tablet after 48hrs and i got my periods earlyon the 11th of last month as normally i get it around the 17th or the 18th but this month when i had sex on the 2nd but as far as i know we had safe sex,  so why my period is delayed and im worried. please advise.