Bleeding after sex??

I recently had sex and had to take a morning after pill. I had just come off my period the same day. It is now a couple days later and I've suddenly begun bleeding. It hasnt stopped since yesterday morning. I know that bleeding is a common symptom from taking the morning after pill and it is too soon to be on my period again, so i am a little concerned as to why the bleeding has not stopped. Any idea what's going on?