Could Brown Vaginal Discharge In The Mid Of Menstruation Cycle Be Due To Pregnancy?

Hi me and my boyfriend had unprotected sex about 3 days ago, january 19. He pulled out before ejaculating. But now its january 22 and i had some brown discharge. My last period started on january 3 and ended january 8. My ovulation date was from i think from january 14 to january 19. Could it be that i am pregnant or what else could it be?