My period is 4 days late after taking plan b 3 days before expected period. i'm not pregnant. i'm cramping. i'm very regular. when will it come?

In 1-4 days: Studies have shown that ECP like Plan B usually has an impact on the period, and if taken early in the cycle, may shorten it or cause spotting, and if taken later, may delay it up to a week. The subsequent cycle may also be either prolonged or light, and unlikely to skip it all together. If you don't get your menses in the next 5-7 days, check a pregnancy test. Please use other protection.