Talk to him about it. And by "it" I mean, tell him what you have accomplished so far. Tell him your story and he likely will not care about your appearance the way you're thinking he will.
It is so much stronger of a thing to fall for someone's personality than their looks. If he fell for only a picture, then this conversing likely would have ended by now.
Chances are, if you tell him your goals and reasons, he will be blown away by your strength and determination along with your pretty face
Plus, he'll be impressed that you are clearly getting healthier for you, not for anyone else.