How soon should your period start after you have taken emergency contraception?

Depends: It depends when you took the pills .Usually you will get your period on expected time if you are not pregnant.

Menses: Potential side effects with emergency contraception can include: tender breasts; changes in menstrual flow (spotting, bleeding, early or late period); loose stools; dizziness; headache; nausea/ vomiting; abdominal discomfort or feeling tired. If you develop chest tightness, difficulty breathing, swelling of lips, mouth, throat – call 911. Notify your doctor if you miss your period. See below.