Dark red blood after taking Plan B????

Stephany

I've had a light period (or at least I think it was) about a few days after I took the pill. (I took it in the same time frame in which I had sex but I used protection during the whole thing). I experienced a light blood flow. But now it's a week later and I just got some really dark blood on my pantyliner. Is this normal? I'm kinda worried...