In most cases, you only need to take one pill. An exception to this rule is women who are over 70 kg or BMI over 26 , who may need to take a two pills if they are using Levonelle or Escapelle.
Each dose protects you only once. If you have unprotected sex or contraception failure again, you will need to take another morning after pill. There is no limit to how many times you can use a morning after pill, even in the same month.