What does it mean if your period is five days late and you saw very light pink spotting once a pregnancy test 1 day prior to when was due came negative?

A negative pregnancy test one day prior to your expected period does not necessarily mean you are not pregnant. Pregnancy tests are not always accurate, especially if taken too early. It's possible you ovulated later than you thought, and your period is simply late. Alternatively, it's possible you could have had a chemical pregnancy, which is when a fertilized egg implants but does not develop. Chemical pregnancies often result in light bleeding or spotting around the time a period is due. If your period is still late, it's important to take another pregnancy test or see your doctor to rule out pregnancy and determine the cause of your late period.