If you are triple negative you should not need to take tamoxifen. It is designed for ER+ people to disrupt the estrogen from causing a recurrence. If you are triple negative tamoxifen will not be of any help.

Definitely change docs this oncologist has no clue what he/she is doing.

You may need to get a second opinion

I had a VERY LOW positive ER, so low that I was treated in my chemo and radiation as triple negative. However, because of the presence of ER+, my onc decided to be extra cautious and put me on Tamoxifen as a precaution. This may be the same case with you as well. Ask questions and don't take or do anything that you're not comfortable with. It's your body and your life.
As for your question, I'm doing fine on the Tamoxifen. The hot flashes were bad in the beginning, but they have subsided. I've been on it for about 7 months now. No weight gain either. Good luck!

You are triple negative meaning female hormones didn't fuel your breast cancer. Tamoxifen is for women who were Estrogen positive and/or Progestrone positive because its a anti-hormonal medication which prevents hormone receptors from connecting to other cells. You were also hers2 negative meaning you didn't have the protein to cause cancer cells to grow rapidly. You might want to get genetic testing performed. Just a thought. I would find someone in your area to get a second opinion.