Lucy, don't get despondent. Unaware people have trouble grasping the concept that anyone could question their gender, as it's a basis of self identification. This is where education comes in. Look for information which might enlighten your wife, and see if you can subtly introduce it. Then look for points in that information which pertain to you and remember them for the discussion you may need to have.
My wife had no concept, but she recognised many feminine aspect of my nature, and while her initial reaction was to walk away, she soon realised she was attracted to my feminine traits as much as my masculine ones. That was 20 years ago. I do, however, do all the cooking, cleaning and such in our household. I guess the challenge would be greater for households with traditional gender role divide.
Allie