Is it obligatory to make up the prayers missed during the first seven days of a menstrual cycle that lasted 15 days? And am I sinful for having abandoned prayer and fasting in the three days preceding Ramadan, due to my assumption that it was menstruation? And how can one differentiate between menstrual days and others, given irregular periods?

The maximum duration of menstruation (hayd) is fifteen days and nights according to the majority of scholars. If the duration exceeds this, the woman is considered to be in a state of istihadah (definition) (non-menstrual bleeding), and she must pray and perform all other acts of worship required of a ritually pure person.

A woman experiencing istihadah, if she has a regular and consistent habit (previous menstrual cycle), should rely on it. Otherwise, she should differentiate between the blood (identifying menstrual blood by its characteristics). If she is unable to do so, she should estimate it to be six or seven days each month, based on the prevalent custom of the women in her family.

If the duration of your menstruation did not exceed fifteen days, your ruling is clear. If it did exceed it, then review the days you did not pray: if they were days of menstruation, then you are not required to make up the prayers; otherwise, you must make them up.

Brown discharge (kudrah) is considered menstruation if it occurs during the accustomed period or is continuous with blood.

A Muslim must inquire about matters of their religion. If they fall short in this despite being able to ask, they must repent and seek forgiveness.