I'm not a doctor, nor do I play one on TV, but my sister and my Mom are both nurses, my sister is actually an OB/GYN nurse. I had the same thing happen with my first pregnancy and my sister told me that you can have false negatives, but you can't have false positives. It can be a sensitive test and need more hCG than your body is currently producing (doubles each day) and show negative, but if it registers hCG, you're pregnant. There's really very, very, very, very little chance of it being false positive.
Crazy.
Me: 42/H: 37 T: 10 years/M: 8 D9, S8 Bomb: 7.23.07 Separated: 1.20.08 D Final 3.19.09 Affair started in '05, found out parts in 11/07. They married 11.26.09