I'll try to explain what I mean. For many years I was thin and saw myself as a thin person. Even as I started putting on weight in my 30s, I still saw myself as slim and able to hide the extra pounds. As the weight continued to creep up, I still saw my thin self in my mirror, even though the scale said otherwise.
It wasn't until one day when I was walking past a large glass shop window and I saw my reflection and didn't recognize that the fat chick staring back was me - that I knew that I had no idea who I was anymore. Now it is the opposite - I see myself as completely obese. I always see myself as the largest woman in the room. It might not even always be true, but I have now internalized my identity as a fat chick. I see myself as heavy all the time.
I wish I had a sense of how I truly appear, but my appearance has changed so drastically over the past 7 years that I have no sense of self.