Weird Period :/

Okay so i have been having unprotected sex for the last few months & started birth control a week or so before i started my period. the first day or my “period” was brown almost black blood/discharge & then the next 4 or 5 days were a normal flow. for the past 3-4 days i have not been wearing a tampon or bleeding regularly but whenever i go to wipe there is almost like a bit of bloody discharge?? i really don’t know what to do. is it my birth control or could i be pregnant? any advice will help! thx❤️