Hmmm....last month I first tested when I was 4 days late and got a BFN. I then tested a week later at 11 days late and got a BFP (it was there but not hugely dark). Unfortunately that one didn't end up sticking. Perhaps you O'd later than expected or it is just taking a little longer to stick and start interacting with your body?

It might be worth a visit to the doc for a blood test if AF doesn't show soon. I've heard some people say that for them urine tests didn't show positive til well into their pregnancy....

Good luck!