The tamoxifen is having an impact on endometrial thickness. This is a common side effect however we would suggest that an endometrial biopsy is done as a routine precaution. It can be done in clinic without anesthetic so is very straightforward and I would suggest that you see a gynecologist for that procedure.
In terms of ongoing management, that would depend on your age and other health. For example hysterectomy would obviously stop the bleeding but is a serious operation when you have other health problems.
Thank you for posting that information. I have not seen it earlier. The report is reassuring in that the texture is uniform and there are no worrying features.
From your research, I am sure that you will read that tamoxifen does have the side effect of unwanted vaginal bleeding. If the norithisterone is not having any impact then I think it is worth discussing a hysterectomy with your doctor. You will be on Tamoxifen for at least another 3 years so heavy bleeding is both an inconvenience and can cause anemia. As well as the increased risk of endometrial cancer with time. In a person who is not on Tamoxifen then there are other options such as ablation or use of hormones long term, but this would not be suitable for you.
At age 52 you are quite young, so the operation should be straightforward and I would definitely discuss this with your doctor.