Talk to Gynecologist on Periods Issue

My periods does not start in normal way .When my date come in first 4 to 5days there is little brown discharge sometimes in a day after these days too much heavy bleeding starts along with much pain in my legs ,back and head .Heavy bleeding last for 5 to 6 days after this again thick brown liquid discharge for 4 to 5 days . Itching remain whole week in my lower body area .My periods last for 17 to 18 days .I consult my gynaecologist and performed ultrasound that was clear.Plz tell me how my periods come normal and how can too much heavy bleeding be controlled.