If i had sex took a pregnancy test and the result was negative then i got my period and now my period is very late, what could be the cause of that?

Can I be Pregnant?: Remember, viable pregnancy stops vaginal bleeding. Thus, having a period represents physical proof that one is not pregnant. Delayed or missed periods are very common in the young. They are usually caused by extremes: extreme dieting, extreme exercise, obesity, poor nutrition, extreme stress and other things that cause hormonal fluctuations.