What is considered menstruation from the secretions and blood in the case of irregular menstruation, especially if a non-Muslim doctor states that what precedes the blood is not considered menstruation due to a health problem?

The woman mentioned is experiencing irregular bleeding (istihadah (definition)), because the duration of the blood, and the yellow and turbid discharge connected to it, has exceeded fifteen days, and there is no period of purity between the two bleedings. As long as she does not have a regular habit or a distinguishing factor, she should consider six or seven days as menstruation, and count everything else as istihadah. So, she performs ghusl (definition) after the days of menstruation, and performs wudu for every prayer during the days of istihadah after its time has entered. She then has all the rulings of ritually pure women.