Hi. my periods are usually for 4 or 5 days but it has been for 3 days for the past 5 months and the last one was only for 2 days. the flow was normal though. what could be the probable reason?

Short periods: The main reason for light/ short periods is change in hormone levels. Causes for what seems to be a light period can include: thyroid problems, eating disorders, excessive exercise, initial periods for a girl, use of an intrauterine device, oral contraceptives, perimenopause & implantation bleeding in early pregnancy which rarely occurs.

Menstrual ?'s: Menstrual flow varies from month to month, and a diminished flow may simply reflect a slight drop in estrogen production from your ovulating ovary, which then influences the thickness of the lining cells in the uterus, and consequently the blood flow at the time of your period.