I cant really pull off statistics right now, but I can tell u nikki is right, there is always a chance with u getting preg any day of the month, meaning even on ur period.
But chances arent that high, though u will still need to take some preg tests to be sure.
So take one a week after ur period, if came out negative, take another one a week later, do that a few times if tests keep coming out negative, for about a month.