hi i am 17 years old i have been on birth control for 2 1/2 years now and i have been on my period for 3 days now and its almost over. normally the first day of my period im very heavy but the first day of this one i didnt start till late in the day and it was brown blood and very spotty. i never have a spotty period. i usually go through 3-5 pads a day and so far in the 3 days ive only had to change my pad 4 times in all three days total. i am currently sexually active and the last time i had sex was about a month ago. am i pregnant?