Did the morning after pill fail and I'm pregnant?

I stayed with my boyfriend on Thursday 15th September 2011 and I took the morning after pill from 5 to 4 pm. I have not yet menstruated. after 1 week did the pharmacy pregnancy test gave negative, then did another with interval of a few days gave negative. Only I feel nauseous ... does it have to be like I'm pregnant? In other words, the pill failed ... and if it failed because the tests give negative?
Expert answer:

First of all you should only consider the possibility of pregnancy if you have a delay of your menstruation longer than 15 days. Another important point is that the symptoms of pregnancy do not usually appear in the first month of pregnancy. It is always important to consider that the morning-after pill causes symptoms like nausea and menstrual irregularity.