Unusual really light brown period, could i be pregnant even tho im on a birth control pill?

I've been on a birth control pill for about three or four months now, and now my boyfriend and i have unprotected sex everytime, only protection being the pill i take every morning. well my last "period" was very unusual. i usually get the regular mild period, but this time it was very light, and brown, like barley even a period. i may have taken one of my pills a couple hours late, then had sex that night. could i be pregnant ?!?!