Even when Cycloreg (norethisterone) is started several days before the expected period, it does not always delay menstruation. The effect depends on individual hormonal response and the exact timing in the cycle. If the body has already begun the changes that trigger menstruation, breakthrough bleeding can still occur despite starting 5 days earlier. Heavy bleeding and cramps mean your cycle has continued despite the medication. Hence, the safest step is to consult a gynaecologist promptly to check your condition and provide the proper treatment to manage the bleeding and pain.