all the symptons of period, but is there a chance or pregnancy??

ok so i had sex wit my boyfriend a couple times a couple weeks ago and recently like 3 days ago. and i know i should be havin my period right about now becuz im a regular and last month i got it on the 21st and today is the 21st. well i got all the signs of my period commin up like my boobs are sore, discharge, and lil cramps. well today i got bad cramps and i saw brown blood or something like that like usual. my first day is usually heavy and so far i have not had much blood at all. more like a quater size!
can i be pregnant!??! im freaking out soo bad!