hi. :)

So, I've had sexual intercourse with my boyfriend on the 26th-27th of this month. I can't really tell the exact time, because it was somewhere around 11pm of the 26th and 1am of the 27th. As soon as we finished, he tells me that I should take plan b for precaution. and that he didn't finish in me, but he's not sure. So immediately, we drive to the store and buy the pill, and I take it... it may have been 15-30 minutes afterward.
Meanwhile, my planned period is on the 29th of this month. And I was starting to cramp the day before, giving me a signal to buy pads, (which lead me into the sex)
I've been having a few side effects, embarrassingly I must say. haha, fatigue, Diarrhea, a little nausea, but no vomiting, and some pain in the stomach.
well, I know so little about the plan b pill; please excuse my ignorance, but, today is the 31st and it's the third day that I haven't gotten my period. Is this normal? If my period is late, when do you think I should expect it to come? I'm sort of in a panic about pregnancy as well, But I've told myself to calm down until I know more about how the schedule and stuff works. Help? :/