Me and my boyfriend had unprotected sex a couple days after my period stopped and I took a plan b within the 72 and I didn't have any side effects even though I usually do. ( This also the time I stopped taking birth control but I had been in it over a year almost two already.) A couple days after the incident we had unprotected sex again (oh and let me remind you that none of these times he finished inside me) and I took a plan b 4 days after the encounter and I immediately start having symptoms the next day. I went to my OBGYN and she said I'm fine but it has been 5 days now of bleeding the flow isn't the same as my normal period but the cramps are. I just wanted to make sure I'm not pregnant. 

PS: I'm supposed to be getting an iud in soon which is why I stopped taking the Birth control I was on.