BRCA1 + Tamoxifen

I'm hoping to find some reassurance from the community. I was diagnosed with breast cancer in April 2019. Lumpectomy in May 2019. Chemotherapy from July to September 2019. Early July 2019 was my last period. I also found out I had a BRCA1 mutation in July 2019. I started Tamoxifen in October 2019. No radiation. Double mastectomy in January 2019.

In discussion with my gynecologist in April 2020, he said I was likely in menopause as my period never came back. This was fine as my next surgery was a bilateral salpingo-oopherectomy and hysterectomy. Then Covid-19 messed up everything.

Fast forward to this past Tuesday and my period starts up. No biggie, I think until I wake up Wednesday morning soaked. By lunchtime I was soaking through an heavy flow pad every hour, so I went to emergency.

My blood work came back normal, so I was prescribed a drug to help with clotting and was advised that I would be called back for a pelvic ultrasound within the week.

On Friday I called my oncologist and spoke to the nurse to give an update on my situation. That's when she said it could be the Tamoxifen causing the abnormal bleeding and that it's good they've gotten me in for an ultrasound quickly (I go on Tuesday). I also left a message with my gynecologist, but haven't heard back.

Now I am freaking out, wondering if I have endometrial cancer. I have most of the risk factors (PCOS, obesity, diabetes, long term birth control use, Tamoxifen, etc.) and I read a couple articles which seem to indicate that a BRCA1 mutation may also be a risk factor.

Has anyone else had a gushing, raging period come on suddenly while on Tamoxifen and in peri-menopause or full menopause? What was your outcome?