I took plan b on the 5th (72hr period) and am currently on day 31 of my cycle which is a slight delay in my period. am i pregnant?

Do a pregnancy test: If negative, repeat it after 5-7 days if still no period

Can't tell: 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. Cycles should return to "routine" after this coming cycle.