WHAT'S WRONG WITH ME

So, the boyfriend and I had sex last night. I'm not supposed to start my period until Monday or Tuesday, I have a 26-27 day cycle and it always comes right on the dot. Apparently he pulled the plug or something and I was bleeding after, but it quit by the time I woke up and I haven't bled at all today.. no ripping, no tearing, just blood.

What in the world would make that happen??