Probably an evap line on the test. You don't bleed if you're pregnant.

Take another pregnancy test with FIRST MORNING URINE if you feel you are pregnant. Read it within the allotted time frame (usually under 10 minutes. Anything read OVER that time, may be an evaporation line).

The test may have been faulty.

it may be implantation bleeding, or it actually could be your period. there are rare cases in which you continue having your period throughout your pregnancy, or you may not be pregnant. you should play it safe and take another test or two.