Plan B side effects

Hi ladies! I'll start with some facts. I'm 21, off birth control and my period has been regular for the last six months or so. This last month I slept with a guy three times with out protection. When I tried to bring up condoms the second time (because Plan B is super expensive) he had asked me if I was on birth control and told him that was besides the point. Yes, I realize I just should have told him no, but I can't go back in time. So anyway I took plan be the first two times. The last time we slept together I didn't bother with the Plan B. I figured I wasn't in my fertile window anyway and I was supposed to get my period today. (This was on Tuesday, 6 days before my expected start date). When I took the pill I had only diarrhea as my side effects. I've had very mild cramping the past couple days but no back aches or breast tenderness, which are usually signs I'm starting my period. I was wondering if anyone has had experience with being late due to Plan B. I doubt I'm pregnant, or at least hope I'm not. I can't think back to the last time I took the pill because it was over two years ago.