It's positive, you just still have low levels of HCG so far. Same thing happened to me this pregnancy, I chalked it up to some tests that technically expired a couple months ago and then dollar-store tests. Anyhow, now I'm 2.5 weeks late, I'm definitely pregnant:)
The brand of test matters. Some are more sensitive than others. You can either believe the ones you took and move on, go out and buy an expensive digital test, buy something like First Response which is supposed to be more sensitive, or buy a handful of dollar-store tests and test every day until it's dark.
Congrats!!