VVVFL?? Doctor's test positive, mine looks negative..

Nan
I went to the doctor today for something non related and asked them to do a pregnancy test because I had some suspicions, although I technically haven't missed a period yet. I'm due for my period on the 11th. Now, I thought that it was all in my head, until the nurse came back and said it was positive!!! I am elated!!! However, I decided to pick up some early reaponse tests on my way home so I can see it with my own two eyes, and have something to show my husband, and it looks completely negative.  So confused. Are the tests at the doctor's office more sensitive? I may have gotten a little too excited and bought my 8.5 month old a "promoted to big sister" shirt too... 
Thoughts?