What is the legal ruling on a woman's menstrual cycle disturbance due to contraceptives, where she sees blood for ten days, then purifies for ten days, then sees blood again?

If a woman's menstrual cycle becomes irregular, she should differentiate. She observes the time she sees the black menstrual blood, known by its smell, and refrains from prayer until she becomes pure, provided that the total days of her period do not exceed fifteen days in the month.