A few times I was four or five days late, tested, got a BFN and then got AF. It's possible that you O'd late and either the first test was too early to get a BFP (or, you could have just O'd late and it's still a neg).
Test again. If it's a negative, test once a week until you get a positive or AF shows up.
This! I only got a BFP after 3 weeks!! I was late for 14 days when I got my positive, I O'd super later and I knew I was pregnant, I never miss my period but the tests were negative. The doctor even told me I was not pregnant and probably my period would just come later, but no, I WAS!! :D
So just be patient and test once every week :D