Im on birth control i got my period for 7 days a normal period when i was suppose to get it when i took my placebo pills after taking plan b and then i spotted for 4 days and then yesterday i had brown stuff but it stopped should i be concerned?

Irregular bleeding: Oral contraceptives contain low levels of hormones that regulate your body's menstrual cycle so that ovulation will not take place. Taken regularly, that is all you need to prevent pregnancy. Plan B has high levels of hormones which, taken after unprotected sex, prevents fertilized embryo's from implanting in your uterus. The high hormone levels disrupt your menstrual cycle and can cause bleeding.