What Causes Spotting After Taking Postinor 2?

Hi I have had few drops of blood everyday since sunday. I took postinor 2 on sunday and on monday the previous week as I had unprotected sex with my boyfriend but I know for a fact he did not deposit in me as I had ejaculated him off. Is this 'spotting' cause of the postinor 2 or am I pregnant. I am greatly worried causing me to feel really sick. Please help me