Could plan b have any long term affects on your period?

Unlikely: While it will alter the next cycle that you have, it is unlikely that it would alter the cycle after that. Most women have normal cycles the next time around.

Highly unlikely: Plan B can effect menstrual cycle but this is not a permanent effect. Some women have reported to their cycles lasting one to several cycles duration. Potential side effects w emergency contraception include: menstrual flow changes (spotting, bleeding, early or late period).