this happened to me once, I wasn't pregnant. But if you were pregnant you would have a few spots once and it would go away, you would not bleed heavily at all unless you had a miscariage, but it doen't sound like you missed a period last month, so I wouldn't worry too much. I would take a pregnancy test just to take your worries away, and if it happens again or you don't get your period next month, go see a doctor.
like kim said take a test
if its negative go to the doctors
it could be a number of things from pregnancy to a hormonal imbalance
no one can tell you if your pregnant. you did not even mention having sex. if your pregnant then simply take a test. it should be correct