Hello, I pills are progesterone pills and they cause harmonal imbalance naturally. Yasmin is combination of estrogen and progesterone ,it can be used as oral contraceptives,its also used to regularise periods . It causes withdrawal bleeding after 3-4 days of stoppage of tablet .All medicines have their side effects and minimal side effects are manageable. If you want to have natural periods you can stop taking tablet but it may take longer period time.