Why Am I Getting White Discharge?

im 21 years old and im having white discharge from 4 years. white discharge is not continuous, it starts suddenly and stops suddenly without taking any medicines or treatment, it also make my cloths dirty.At that time i was in 12th standard and i became very weak at that time. 3 years before i consulted with the gynacologist she had given me a syrup to take for twice a day. After taking that syrup i got a new problem i.e. i was having periods twice in a month. after that i stopped taking that syrup and i didn't take any treatment. Now white discharge starts suddenly and is stopped also but it is in less quantity as compared to 4 years back. im worried why it is happening, do i have any disease plz suggest me