Help with Fareston

I started taking Fareston (I have the genetic mutation that I cannot break down Tamoxifen in my Liver) and I feel terrible!
I thought the hotflashes and moodiness would be my issue but my issues are so much worse than I ever imagined.
I do not sleep. I cannot get to sleep. Once I do, I sleep a few hours and then start with these horrible vivid nightmares. It's almost more like a rest and not true sleep.
I take. 25 of Xanax every night and that is not helping (I've been on Xanax for years).
In addition to the sleep issue, I feel short of breath when I take the Fareston. I have only taken a full pill once and I will never do that again. It was so bad, I thought I was going to pass out. I called my Dr.'s office and all they said was "keep taking it, your side effects will go away". I do not like taking them and in fact, last night I did not take my 1/4 of my pill. I slept like a baby and feel great today!

Has anyone else had problems with Fareston? If so, how did you handle them?
Are there any alternatives to Fareston?

I am due for a hysterectomy/ooph here shortly. They want me on this Fareston for the next 10 years. I can't even get through 10 days! Help!