Im on the pill and have been for years. i had sex 9/16. i got my period the day expected and bled for only 2 days (normal flow) but stopped today. i took a pregnancy test and it came back negative. weird period or possibly pregnant?

Tests are accurate: Birth control pills, when taken each day at about the same time, are still working to prevent pregnancy, regardless of whether the withdrawal bleeding is lighter than expected, heavier than expected, or intentionally prevented. However, if the withdrawal bleeding is unintentionally missing, one can check a home urine pregnancy test (accurate by 3 weeks after sex).