Talk to Gynecologist on Period Issue

My periods does not start in normal way .In first four five days when my periods come there is little thick brown discharge sometimes a day after these days too much heavy bleeding starts which lasts for 5 to 6 days after this agin there is thick brown discharge for 5 to 6 days .In these days there is too much pain in my legs ,back and head and it also coughs when my periods start.I consult my gynaecologist my ultrasound was clear.In this way my period last for 17 to 18 days .In normal days there is too much white discharge.Plz tell me how my period start in normal way and how to control heavy bleeding.