First, congratulations on your 2 stone weight loss - that's brilliant!
Although insensitive, I wonder if your partners comments about his few pounds weight gain are because he's feeling insecure? Perhaps he's worried that you're not attracted to him anymore?
Your post suggests that the disconnection you feel from him may go deeper than a (lack of) regular sex life?
You feel that he hasn't supported your weight loss / health journey, and (although I don't dismiss for a moment your lack of body confidence) do you feel that he finds you attractive? Does he tell you so? What aboutvice versa?
I just wonder if you've both lost the magic that comes from actively cherishing each other...If you can talk openly and peaceably with other, you might find your way back to intimacy in ways that you both find fulfilling and are both comfortable with.
Think back to when you first started your last relationship, all those little things that you both said and did which increased desire, made you feel wanted. Not to mention how you might be splitting household chores, stress you might be under...
Intimacy and cherishing each other are so entwined, perhaps if you felt greater emotional intimacy you might start to trust that you can enjoy being physically intimate with him again? After all, he clearly finds you attractive and you him. In your opinion, your current weight makes you unattractive; in his opinion, it doesn't.
Re being intimate- there is also more than 1 way to skin a cat!
I don't want to sound twee in saying that you should be proud of yourself, but you ought to be - if losing weight were easy there wouldn't be a multi-billion industry around it.
Final thought- attraction isn't just based on a physical whole , it can be the way someone smiles, they way their eyes light up when they talk of something they're passionate about, their intelligence or how sweet they are to stray animals etc! I'm sure there is a myriad of ways he finds you attractive that have nothing to do with a number on the scales - and you should recognise your own characteristics that make you uniquely and wonderfully you :)