Bleeding while taking the pills

Girls, I need to know if having vaginal bleeding it's normal while I'm taking the pills. I mean, I've been taking those for three weeks, and me and my boyfriend usually "play" without the condom in the preliminary part. Today, in the morning, the blood was just a little, and it was like pink, and now, it was just brown blur. It worth mentioning that the pills I'm taking acts imidiatly according to my doctor. Please, help me. Say that it's normal and that's not pregnancy