Had my first period on jan 28 had sex on feb 23..im usually on 30 day cycle..havent had my period yet..what could be the reason.thanks?

No period whats up?: - if you aren't using birth control - pregnancy would be on the top of my list. At this point you are 3 days late - while its still within reason you are going to get your menses - you need to take a pregnancy test. IF you are using birth control faithfully and correctly - then I would give it another day or so - but still take a test if you go another 3-4 days without starting.