Most Helpful Guys
Guys have preferences, you can't say all guys are shit just because the one you have now thinks you're too fat. You can just leave him, and find someone who loves you the way you are now, or you can do what he says in hope that you'll stay together.
I personally wouldn't date a girl I find fat, but that's me. I simply don't find it attractive.
Most Helpful Girls
Dump his ass. That's toxic and abusive. You've told it hurts you and he deliberately says it knowing it hurts you. Find someone who appreciates you for you. A boyfriend should raise you self esteem. He should find you sexy. If he's putting you down and trying to change you then he's a waste of you time. Lose weight for you girl, not to conform to such arbitrary beauty standards of one misogynistic idiot who can't appreciate what he has: you.
People treat us the way we allow them to treat us. You shouldn't be keeping up with this @s*hole, Dump him, then lose weight for yourself, not some jerk. And find a new guy before getting thin or in your targeted shape please so that this time you don't end up with someone who doesn't care for you enough or love you for the beautiful person you really are!! You will surely find guys who are not shallow enough to make you feel that way about 'losing weight', you are capable to find someone who'd encourage you enough!