Why The Periods Are Delaying?

Q:Hello sir, i am 24 yrs old.i had sex with my bf for the first time.he ejaculate outside.after 45hours i took unwanted 72 on 25may.my date of menses was also the same 25 may.usually my periods delay 2-3 days.bt sometimes it delay upto 1-2 weeks.i didnt get my menses uptill now.i m feeling very normal.i dont have pain anywhere.plz help me.either i m pregnant or not.delay of my menses is normal or something serious.