@gails
I would recommend that you discuss this with your oncologist before taking any supplements, and especially something which contains progestin (progesterone). Do you know your Progesterone Receptor status? I would imagine that it would be an important part of the discussion.

As to being concerned about the side effects of anastrozole before starting it, you might want to wait and see how you react to it. Not everyone has side effects from it; some side effects are quite manageable; some even go away after a year or so, as your body adjusts to it. Keep the faith, and always keep your oncologist in the ongoing, multi-year dialogue!