I too am encouraging you to be assertive about folowing up on what could be early stage uterine cancer. I am concerned that your ultrasound may not be completely diagnostic at this early stage.
I have stage 3 uterine cancer along with stage 1 ovarian on both sides. My ultrasound only diagnosed the ovarian cancer by way of seeing a complex mass on one ovary. There was no mention of the uterine cancer or a cancerous second ovary by the ultrasound technician. Apparently she didn't see the uterine cancer so imagine my surprise when my pathology report came back so skewed toward advanced uterine cancer that had invaded 75% of the myometrial wall.
I am pre-menopausal so my symptoms were heavy bleeding at age 42 which I failed to think could be anything but pre-menopause.
I strongly urge you to find someone to do a uterine biopsy. You should NOT be bleeding at all post-menopausally.