What Causes A Vaginal Discharge After First Unprotected Intercourse?

i had a unprotected sex with my boyfriend after 12 days of my last period and suddenly i took i pill with 1hrs after having a sex then after 1 weak later, i am getting brown color vaginal discharge.Does this mean i am pregnant ?? OR is there any chances of having disease/infection inside my vagina? or the brown color vaginal discharge is the result of taking i pill? And this was my first sex with him before i was virgin