Starting period after 3 years of cancer treatment

I was diagnosed with cancer 3 years ago October 2001. I did not have a period and was put into menopause because of chemotherapy and radiation. After 24 months my doctor switched me from Tamoxifen to Aromasin that was in July 2004. Today January 3, I started my period after 3 years and 3 months. I was wondering if anyone else has had this problem? My cancer was Her 2 positive also. Thanks for your input.