Chemo-induced menapause, what drug to take?

Hi
I am 42 years old and ER/PR/HER2 positive.
I finished chemo last June.
I am on Tomaxifen, because I was premenapause before chemo. The chemo put me into menapause. wondering if anyone has experienced this ??
I was on herceptin but my MUGA scan went from 51% to 36%, so now I am on heart medication and hopefully my heart will get back to normal so I can go back on herceptin.
Thanks
Bonnie T