A 32-year-old African American woman presents to the outpatient office complaining of constant pelvic pressure with low back pain for several years. Her menstrual cycles are described as heavy and prolonged. Last menstrual period was ten days ago. Obstetrical history is significant for one full term pregnancy and two subsequent miscarriages. Gynecological history is significant for first menarche at the age of nine years. Family history is negative for gynecological malignancy. Physical exam reveals a firm, mobile, enlarged, nodular uterus. What is the most likely diagnosis