If your last period was on January 20th, it is recommended to wait at least a week after your missed period before taking a pregnancy test. This allows enough time for the levels of the pregnancy hormone hCG to build up in your body and be detected by the test. However, if you are experiencing any early pregnancy symptoms or have reasons to suspect that you might be pregnant, you can take an early detection pregnancy test as soon as five days before your expected period. Keep in mind that the accuracy of these tests may vary, so it's always best to confirm with another test if you get a negative result but still suspect you might be pregnant.