Pregnancy tests can start to show results when you take one 10 days after ovulation, which is usually four or five days before you would expect to miss your period. Many OB-GYN doctors and midwives recommend that you wait until the day of a missed period, and ideally 3-to-4 days after so that you can be sure the test didn’t just fail to detect low levels of hCG. Even then—and even with the best pregnancy tests on the market—it’s possible you won’t not see a positive result until closer to a couple weeks after your missed period. The longer you wait, the more likely a test is to be accurate. After two weeks from your missed period, if you get negative results, chances are you are not pregnant. If you still believe that you are, you should talk to your healthcare provider.