if ur period is late then taking a test right now is very helpful..
tests r quite accurate after missing ur period..
but as Tara mentioned, it all depends on how regular ur periods r and whether u were ovulating at that time or not.
the Plan b pill doesn't always work I suggest using a condom with BCP if u dont wanna get pregnant...
Good luck
If your periods are like clockwork, being a week late would be out of the ordinary. But if you have irregular periods I wouldn't worry. I think your chances are low because of when you had sex and the fact that you took the plan B. I would wait for your period. If you don't get it by the 18, Mon. I would test.