In the end it has to be your decision. I ended up with a mastectomy anyway but my question at the time was whether I should have both taken. The answer then was that it wasn't needed. Twelve months later my surgeon said that if I was really struggling with the anxiety, he was happy to take the other. I haven't done it but know that I have that option without having to fight for it. If it is what you feel you need to do and your surgeon won't consider it, best to find someone else.
By the way, do you have a 3D mammogram or a 2D? 3D gives more clarity.