I Had Breast Cancer Last Year And Am Currently Done

I had breast cancer last year and am currently done with the chemo and radiation treatments, after I requested a double mastectomy.
My cancer doctor has me on tamoxifen. The medication has made me very sick from the beginning. I was told by as friend that I can ask my doctor if there is another drug that can help in a similar way and not give me the bad side effects. What would you advise?