This is so tough. I think the real problem here may have nothing to do with weight.
So, backstory: my Fiance once bumblingly told me something which I found appalling — he was looking at a photo of some models and said, “That kind of build is so beautiful, don’t you think?” Now, I’m not overweight but I’m not skinny, and my frame is such that I never will be. I’ve got wide birthin’ hips, let’s just say! LOL. And my Fiance, before me, had dated someone who, by virtue of her frame and genetics, is tiny, tiny, tiny – like a model. SO, I was NOT pleased, and let him know how it damaged my confidence. He was horrified at the fact that he’d made a comment like that. Anyway, one day, as a follow=up no doubt, many months later, he said to me, awkwardly, that his taste in female beauty had changed – that now he found his eyes catching on women built like me. This time, my BFF was appalled but I found it kind of sweet. I knew what he was saying, and it rings true with my guy friends’ remarks — that when you find someone you love, your tastes change; THAT person, your beloved, becomes your new ideal of beauty.
Don’t get me wrong, my Fiance never should have told me a) that he found MODELS’ bodies attractive (I mean, DUH) or b) that he was looking at any other women! But his intentions were pure (I say this because both remarks are memorable precisely BECAUSE he has never ever hurt my feelings in any other way) and I got over it pretty easily BECAUSE he is constantly telling me, and showing me, how attractive he finds me.
Your Fiance said something to you that hurt. That’s human, we make mistakes. But it sounds like that comment comes in the context of a relationship that, more broadly, makes you disposed to insecurity – about yourself, and his feelings for you.
I guess what I’m saying is: consider his remark, and your own reaction to it, to be reason to give SERIOUS THOUGHT to whether you feel loved and prized and valued and cherished in this relationship, overall. If you do, then his remark about your weight is something you should be able to talk about with him – how it made you feel, how it makes you fear for the future (because age and pregnancy, if you want ot have a kid, brings a new set of challenges to weight maintenance).
But if his comment hits on insecurities you ALREADY had in the context of the relationship, then I’m going to agree with some of the other comments above: it could be a real sign that he is not the guy for you.
I know that’s a hard thing to even consider, two months before the wedding. But you owe it to yourself to consider it, if this isn’t the first, or second, or even the fifth time he has made you feel judged and found wanting.