If you used protection (that did not break) I doubt that you are pregnant. However, there is always a possibility. I would suggest that you wait another week. If you still have not received you period then take another test. If it is negative, then it will be time for you to contact a doctor.
Have you gained/lost weight? Changed your eating habits? Started/stopped/switched birth control? Are you under an unusual amount of stress? All of these things can affect your cycle.
You may get a better response if you post this in the "Am I pregnant?" forum.
I hope you get the results you are looking for. Keep us posted!