Plan B Pill

So we had a slip up and the condom slid off during sex. I don't think it happened until after he finished. It was still inside me, and seemed like it was straight (so it didn't look like any semen spilt inside of me), but I took the plan b pill about 17 hours after the incident. My period was supposed to start 3 days after the day I took the pill, but now I'm 3 days late. (Took the pill Saturday, was supposed to start Tuesday, but now it's almost Friday with still no period). I'm not completely regular anyways, but would the pill throw off my cycle? My boyfriend is beginning to worry and so am I. I plan to take a pregnancy test in a few days, but what do you think?