What Causes Spotting, Headaches And Light Headedness After Periods?

I just had an 7 day period which ended on sunday and Thursday I had a little spotting. Today (Friday) i have more spotting. I ve been lightheaded, tired and have had headaches on and off since the end of my period. I had unprotected sex Saturday and Sunday but took a morning after pill Sunday afternoon. Please help. I m worried.