Plan B question. Input appreciated.

I know plan b is NOT a form of birth control and I don't use it as one. Recently I had a slip up and used it for the first time ever. I freaked out because my period is more than a week late. But I took a pregnancy test and it was negative. I guess I'm just getting paranoid. I wouldn't mind being pregnant as I have a good support system but I don't want to be caught off guard by my period. If you've ever had a similar situation all stories/information helps. Did it result in pregnancy? If not, How long before you got your next period?