What kind of relationship do you have with your doctor?
Do you feel that he really listens to you?
I see in you an absolutely desperate woman, I would venture to say you may be depressed and there may even be times when you don't want to look in the mirror. This is not healthy.
I think you doctor needs to know this as well as seeing your food & exercise diary, you may need to see a specialist. You don't have to "resign yourself to being a healthy big person".