Started my period after 5 years of medical menopause

Hope40

I am approaching my 5 year mark and if that isn't stressful enough I also started my period. Once chemo started it shut down my ovaries and I haven't had a period until today. I called my oncologist and he told me not to worry that my body could have started producing more estrogen and could have triggered the period. I am ER/PR-, HER2+++ positive and was diagnosed at age 38 IIIA. I am very worried. I recently had my pap smear and it was normal. I have looked on the internet but no information is available. It simply states most you women will start there period 1 to 2 years after medical menopause. Any advice or information