What Causes Missed Periods With Vaginal Soreness And Clotting?

Last weekend me and my boyfriend had sex alot over 2 days, we didnt always wear a condom but im on the pill and i take it at the exact same time everyday. After the weekend i have been sore down below which i assumed was normal but after 5 days i have been getting little bits of blood coming out. I have skipped my period the last 2 cycles. Would you be able to help me figure out whats going on? Thanks