Must I pray if my menstrual cycle has become irregular, so that it comes for 7 days and returns for 2 days each month after childbirth?

If the blood ceases after seven days and then returns two days later, the returning blood is considered menses as long as it falls within a period suitable for menstruation and its total duration, including the interruption, does not exceed fifteen days. If the blood stops, you must perform ghusl (ritual purification bath) and pray. Then, if the blood returns, you are considered to be in a state of menstruation again. If the bleeding continues for more than fifteen days, you are considered to be in a state of istihadah (non-menstrual bleeding), and you should follow the rulings for a woman in istihadah.