You can retest in a few days if you don't get your period.
Personally I am a pregnancy test aholic! I take one every morning until I got my BFP! Honestly "they say" that if you are late for your period by a couple days and its negative then wait until 2 weeks after your period is due to re-test. Many docs don't tell you to even test until two weeks after your period.
If I was you I would test on the 24th, which would be a week late on your period and if you get a negative then wait one more week to test. If you still get a negative and don't have your period yet then call your doc and they will draw your blood and test the hcg levels in your system. If you wanted to you really could even call your doc now and do that! Hope that helped!