What are common side effects of plan B

My boyfriend and I had sex Feb. 18 and the condom did not break, BUT before and after sex we were just laying in bed for a while and fooled around for a bit. I was really cautious to not let his penis get close to my genitals because I am aware of precum. Point is I don't exactly remember if he got super close and that's when I started psyching myself out. I also have irregular periods so that didn't help! I am planning to get on BC even if we're waiting for a little longer just to be ready and not freak out like this time when I really am ready (I already have an appointment for it next week)

But anyways I freaked out. Perhaps realizing that I wasn't entirely ready to have sex, because I mean, you're not supposed to freak out and take plan b if you're ready. I'm aware that it also maybe was not even necessary.. I took the pill (24 hrs. later) and felt no side effects and was worried something may have gone wrong. About 5 days later I got a really heavy period (went through a box of tampons heavy) it lasted about 5 days. Now two days later,after my period, my boobs feel really tender more so around my nipples. Once again, I am freeeeeaking out. Is this normal because of the hormones creating an imbalance or because its still in my system or whatnot? Will it go away or is it what I fear? I confided in a close friend and she says that the heavy period almost guarantees that everything is okay, is that true also that the tenderness I feel is just the huge amount of homornes? I need someone to really give me advice and peace of mind, even if it comes through a lecture.