I used postinor 2 twice in one menstrual cy cle. how long should i wait until my period comes again, and if it skips, how many cycles could skip?

Postinor 2: Potential side effects w emergency contraception include: menstrual flow changes (spotting, bleeding, early or late period), nausea, vomiting, dizziness, fatigue, headache, breast tenderness & abdominal pain or cramps. Take pregnancy test & notify dr if your period is 7 or > days late. You may or may not have changes in bleeding or skip a period. We have no way to predict.