Possibly pregnant?

So, my boyfriend and I recently had unprotected sex for the first time. It didn’t last long and he never finished. I was scared and so I took plan B about 15 hours later. I took plan B the day I was supposed to start ovulating. However, my period has been really wack and very late the last few months. I just want to know what the possibilities are here. *EDIT*Only took plan B once, had nausea and slight cramping after taking plan B