If you are more than 1 week late at any time for your period, and not showing up on a pregnancy test, you should always contact your dr. They can give you a blood test to make sure you really arent pregnant. A pregnancy test will show most pregnancies, but there are some cases, like in some rare tubal pregnancies, that you dont have enough hormones to register on a pregnancy test, and its important to get it check out. If you have always had regular periods and are now having irregular, you may want to call and see your dr anyway as something else could be going on.