Talk to Gynecologist on Pelvis Scan,disturbed Period

from last 2 years ,I m having disturbed periods. bleeding is Very less and prolonged.Cycle becomes irregular.Duphaston was advised by the doctor.After taking duphaston for 11 days got severely heaving bleeding when It is stopped.but this problem reoccurs after a few months Doctor has advised for pelvis scan.Which type of further testing or procedure should be adopted.kindly advise.