Can I Pill Cause Delay In Periods?

i HAD MY LAST PERIOD ON 25TH DECEMBER. N THEN I HAD A SEX TWICe i.e ON 27TH JANUARY AND 30 TH JANUARY. BOTH THE TYMS I HAD AN IPILL WIDIN 24 HRS. I HAVENT HAD MY PERIODS TILL DATE. I DID A HOME PREGNANCY TEST ON 2ND FEBURARY N FOUND IT OUT NEGATIVE. M I PREGNANT OR IS THIS THE SIDE EFFECT OF AN IPILL? PLZ HELP.