Hello and thank you for posting. 

It can be difficult coping with the side affects of the surgery and the hormonal treatments used in breast cancer.  The unwanted weight gain despite being healthy and taking exercise is frustrating and I'm sure doesn't help your emotional strength. I've placed here information on living with these symptoms. 

HRT post a breast cancer diagnosis and can be complicated for the reasons you understand. I've posted here a link to the 'Breast Cancer Now' page on menopausal symptoms, but this charity also has a forum in which you would be able to hear from other women maybe in a similar position to you and get their view. Here is the link to their forum.

On the NHS website they talk about anti depressants as an alternative for certain menopausal symptoms, but again good to talk this out with your GP.

Take care and I hope you get the information you need. You may find it helpful to talk things through with one of the nurses on our helpline.  The number to call is Freephone 0808 800 4040 and the lines are open from 9am till 5pm Monday to Friday.

Sarah.