If your last period started on January 13th and you suspect you might be pregnant, it is recommended to wait at least a week after your missed period before taking a home pregnancy test. This will give your body enough time to produce detectable levels of the pregnancy hormone hCG. However, some sensitive tests may be able to detect pregnancy as early as 7-10 days after conception. It's important to follow the instructions provided with the specific brand of test you choose, as different tests have different sensitivity levels. If you take a test too early and get a negative result, it's possible that you may still be pregnant but tested too soon for accurate results. In such cases, it is advisable to wait a few more days and retest or consult with your healthcare provider for further guidance.