My period is due in about 2 days, it usually arrives on the by the first of each month.
I taken plan b, about 12 hours ago, and haven't experienced any symptoms of the pill doing it's thing.

my questions are:
what are the chances, and how safe am I for taking plan b so quickly?
will my period coming have any effect on that percentage?
how long does the pill stay in your system?
when should i expect to feel symptoms of the pill?