Irregular spotting after taking plan B

So, its been about a month but in that duration I took 2 plan B bills, I'm guessing about a week or two apart and since then my body doesn't feel the same. About a week later after the second pill I experienced what I THOUGHT was my period (duration of 3 days). I've been experiencing sporadic spotting along with cramps and sore breasts, but I took a pregnancy test two weeks ago and it was negative. I'm kind of freaking out bc I don't want to be pregnant. HELP!