What Does Delayed Periods After Unprotected Sex Indicate?

Hi so I wanted to know if there s a chance of me being pregnant I had sex with my fiancé about three weeks ago and did not use protection although he did pulls out and came five minutes later, my period was suppose to come in on the 14th of this month and now it s the 18th and my period is fairly regular, but my eating habit have changed in the last two weeks also which I know may affect my period I ve cut back on rice completely, during the past three days I ve checked and have had no spotting but when I checked my cervix I found blood could there be a chance that I am pregnant ?