A fat person is fat (medically, obese or probably morbidly obese as the threshold is surprisingly low!). Fat sounds much nicer than morbidly obese.
Curvy doesn’t mean fat. Curvy means curves in the ‘right places’ i.e. hourglass figure. Sometimes fat people use curvy to feel better about it, but all it does is muddy the waters.
A huge % of the population are fat.
It is a description. Not a declaration of war.
You have a mirror. If you are fat, you will know you’re fat, the same as you know you have black hair, brown hair, blonde hair, whatever colour eyes. This wasn’t a bombshell.
Being bullied for being fat, as awful as any bullying is, is not the same as being bullied for characteristics that you can’t change. If you hate being fat so much, you can change that. If you don’t want to change it, you need to accept who you are and love yourself for it. But you can’t be upset that someone comments on you being fat, when you say yourself, you are fat.
Your partner is clearly the problem here. I do not believe in a million years that his parents just created this out of nowhere. He’s obviously expressed these views in the past, and is now desperately trying to stop you hearing that fully from them. So he’s blocked them, like a child, for discussing between themselves that it’s a surprise to see he’s veered from his long standing aesthetic preference. I think you should take a good look at yourself here though - are you rubbing your own insecurities and past upsets off on him so that he’s genuinely terrified of you finding out he ever expressed these views? You’re fat and he loves you, so I don’t think it’s at all relevant. He loves you so much that he’s thrown himself in head first for someone who’s not his usual type. He’s stopped being so shallow. That’s a positive.