I got a light period, late,after plan-b.now the second period is late by 2 days and i have very little brown discharge and vaginal farts.is it normal?

Maybe normal: Plan B can alter the menstrual bleeding for the cycle in which Plan B was taken, and sometimes the next cycle too. One should be sure to check a home pregnancy test about 3 weeks after sex, because Plan B works most of the time, but not all the time. Be sure to put a reliable "Plan A" into action, so that Plan B won't be needed in the future.