Brown discharge? Yasm�n contraceptive?

Hi, today (June 28) its my third day of the week im supposed to have my menstruation. I got a brown discharge with a little stomache before, it was very dark and a little thick and some bright red. No more discharge has appeared. I had relations 20 days ago (8 june) without preservative, this is my third month taking Yasmin, is there any chance i got pregnant? or why is my discharge brown and poor? could it be implantation bleeding? Thank you!!