Getting a pregnancy test would be the first thing to do to make sure.
However, there can be other reasons why your period is late. Stress and anxiety can cause delayed ovulation which in turn would make your period later than usual. Losing or gaining a significant amount of weight can also cause you to miss a period. Also, make sure that you counted your cycle correctly. The first day of bleeding is the first day of your cycle. Count from cycle day 1 until the 28th day. This will give you an estimate of when your period will arrive. It is normal however, for your cycle to be anywhere from 21-35 days apart. Your period can vary, especially during the first year or so of having your period. If it turns out you are not pregnant and your period continues to be irregular, you should talk to your health care provider to see why this is happening.