Does he know about the body issues, aside from you telling him to find someone in better shape? I've found he's the only person who knows how hard I'm working and listens to me when I'm ranting about the darn cookie I ate. But he's equally as excited to hear me talk about dropping a dress size, and I'm actually comfortable telling him my weight now.
If all you say is true, he obviously loves you and just remind yourself of that. Tell him you need support. My boyfriend leaves me notes and this guy could do that for you. example: "lost over 5 stone, go hot mama!" I know it seems silly, but little bits of encouragement when you least expect it is lovely.
And like critter said, if it's really a problem, maybe think about couseling or seeing a dietican/nutritionist; someone who will understand how you feel. Hang in there, find yourself, love yourself, and be happy!