What Is The Reason Of Bleeding?

I m an 18yr old female. on 1st of this month, I had sex with my bf during which the condom bursted and before we could have realised, he had ejaculated inside me. so i took an ipill. It was the 5th n last day of my periods. however, yesterday i.e. on 4th while having sex, we noticed a brown colored vaginal discharge and now I ve started bleeding as i normally do during periods. What might be the reason for it? Is it normal? Please help.