What Causes Delayed Period After Taking Plan B Followed By Sex?

I had an abortion recently. I had sex but he was wearing a condom ,once we finished like his cum was coming out the condom. So itook a plan b pill . Ihad my period feb5.2015 . Ishould have started my period yesterday march5.2015. Ifeel like im going to start with having cramps and feeling like something is coming out but isnt blood . Whats going on?