If i take plan be a week before my period, will it make my period late? i'm 4 days late now and not sure if it's due to stress or plan b or pregnancy

Plan b: you need to use plan B according to instructions and for the correct reason. I would not worry about whether your period will be late unless it's from being pregnant .

HPT: Potential Side effects w emergency contraception include menstrual flow changes (spotting, bleeding, early or late period). Take pregnancy test & notify Dr if your period is 7 or > days late. The ultimate way to determine pregnancy is via a pregnancy test - but would wait a couple weeks since intercourse to test.