I was having bleeding during periods for atleast three days but from last four months i hardly bleed for one day during periods.i am 31 years old. ?

It may not mean anything specific.: If your menstrual periods are still regular, it may not mean anything specific. On the other hand some hormonal disorders such as PCOS and hyperthyroidism may result in changes in menstrual flow. If you are on birth control pills and have changed to a different estrogen preparation this can also be a factor. At age 31 I am not suspecting premature menopause without other history. Suggest GYN eval.