Is it obligatory to fast when menstrual bleeding occurs intermittently after stopping contraceptive injections?

If the blood discharge and the interspersed period of purity exceed fifteen days, then it is considered istihadah (definition) (non-menstrual bleeding). If she has a previous regular habit, she should stop praying and fasting for the duration of her usual habit, then perform ghusl (definition) (ritual bath) and wudu (ablution) for each prayer after its time has begun. If she does not have a regular habit but can distinguish between menstrual blood and other blood, she should consider the blood she identifies as menstrual as such, and perform ghusl after it ceases. If she has neither a regular habit nor a reliable distinction, she should consider her habit to be six or seven days. However, if the total duration of blood discharge and purity does not exceed fifteen days, then all of it is considered hayd (menstruation). If she experiences a period of purity during this time, she should perform ghusl and pray. If the blood returns, she reverts to being in a state of hayd. It is important to note that the disturbance of one's menstrual cycle is among the side effects of using birth control methods.