Hi Doctor I M Having Menstruation For 13 Days .

Hi doctor i m having menstruation for 13 days . Bleed is very minimal since first day till 13 day. It is so less that even it does not require use of pad. This has not happen earlier . Earlier i miss one period on may after that it was normal and now this month menstrution pattern is like this my doctor sugested to take trapic mf .,i want to ask why is this ocurring what could be problem plzz tell me