I menstruated on the 17th may 2011, on the 27th of June 2011, when i whipe i saw the blood but not too much of?

i menstuated on the 17th May 2011, but my menstruation delayed and on the 27th June 2011, when i whipe i saw small drops of blood and today is the 28 of June and i still see that smll blood, but it doesn't come out like normal menstruation, then i tested but result were negative does it mean i could still be pregnant????? please help