Actually, a missed period is one of the most important early signs of pregnancy, yet your period being late does not always mean you are pregnant. It might be caused by hormonal imbalances, which influence your menstrual cycle by preventing ovulation and subsequently menstruation.
If a woman wtih a possilibty of being pregnant has a late period they should do a pregnancy test. If you get a negative result, our advice is that you take another one after 4 to 5 days. If it is negative again, it means that you are not pregnant.
Should your period be missing the following month too, it is strongly recommendable to visit your gynecologist, so that you can have your hormonal levels evaluated with a blood test. If the presence of hormonal alterations is confirmed, your doctor will decide what is the best treatment to regulate your cycles.