Hello. I Had My Periods On 12th January. I Had

hello. i had my periods on 12th January. i had unprotected sex on 22nd January. i took i-pill on 23rd January. i Have started with my periods (if they are my periods) on 31st January. is it my periods or something else? has my menstrual cycle changed? what will it be if it has changed? my cycle usually varies from 26-29days . please help me clearing my doubts