How To Regularize My Periods?

hi doctor.. i m 27 yrs old.. my periods are not regular.. and it lasts for only 3 to 4 days. i consulted with doctor when i was 20 . She gave me few medicines .. then i had my regular periods.. but after few years the same problem occurred again.. i take Ashokarist.. Please suggest me some thing.My height is 5.2 and my weight is 46.5kgs