PLAN B!!

Ok, so I'm freaking out because I had sex with my boyfriend a week ago & he didn't pull out in time. So I took a plan B the same exact day. My period ended 4 days before this happened. now today I went to the bathroom to see that I was bleeding. IM FREAKING OUT!! Because I don't know why I'm bleeding. is this normal? I'm really scared, please if anyone knows something, help me