According to your data you should have had your period around the 3rd of March; your period is about a week late. A late period is the first sign of a possible pregnancy. It is an unreliable sign, however, and needs to be confirmed. If pregnancy tests results are consistently negative, you are probably not pregnant. Reasons for lack of menstruation can be numerous but most often are related to physical stress and/or a hormonally active ovarian cyst. You can go immediately to your gynecologist for an ultrasound examination of the ovaries.