What Causes Heavy Bleeding During Periods And Prolonged Periods?

hi. i'm 40, 168cm in height, weighing 135lbs. my problem is my heavy bleeding during menstrual periods, prolonged mens, with spotting in between periods. ultrasound report is that i have an enlarged retroverted uterus with thickened inhomogeneous endometrium, submucosal myoma (encroaching the endometrial stipe>50%) located at the lower uterine region which measures 3.3cm x 3.2cm. unremarkable uteries, adnexae, cervix and posterior cul de sac. doctors, what should i do. please help.