plan b question.

I'm not sure if this is the right group to post in and if it's not, I'm sorry in advance. Last month on February 16th, I took the plan b pill. I had some light spotting that turned into a pretty much normal period, except quite a bit more painful. After that I felt normal, but it was not a feeling I wanted to feel again. Especially any time soon.

On March 4th, my boyfriend and I had sex and he came inside me. It's not the first time it's happened and I didn't end up getting pregnant. I did not want to take plan b again and the whole reason and situation as to why why I took it, changed. So I didn't end up taking it. On the 10th of March, I got what I swear were implantation cramping, my breasts were so sore, my nipples were constantly at attention (that like never happens, unless it's cold or he's playing with them, even then, they were not this erect.) I got nausea and felt like I could throw up but never did. The worst by far is the heartburn. (We have a six year old and I have only ever had heartburn when I was pregnant with her.) I kept checking for implantation bleeding, but nothing. I have been having off and on mini cramps since, none are really painful, its just so strange and last week I was incredibly tired. Normally I am a night owl and stay up pretty late. But last week, I kept falling to sleep at 11, after having a mid afternoon nap.

My period was due yesterday and nothing. I took a pregnancy test and it's negative. Am I just still feeling the remnants of the plan b pill? Does it stay in your system that long or just mess up your period? Have any of y'all who have taken it had these feelings the next month?