Try doing things to make him feel wanted- words sometimes are not enough. Maybe you don't go out in public together enough, maybe oyu've not introduced him to people who matter, try complimenting him in public- in the midst of your friends...just some ideas

Seems like what my wife goes through once in a while. It's obvious he's very insecure about himself.

Hopefully, you don't look at other guys and think their hot, because that would probably worsen the situation.

Compare him to other guys similar to him, and tell him "You look as good as him!" or something. This may backfire though.

Show him how much you think he's attractive. Don't just complement him, LUST for him. And do it often. Go crazy over him, and obsess over him. Tell him what you like about him during sex or something. Tell him "I love it when you do that!" or "I love seeing your (fill in)". make him feel good about himself. Have fun, and get turned on! :)

When he is having a bad hair day, be honest and tell him to fix it. If he asks you "Is my butt getting big?" if it honestly is getting too big, tell him "yeah... but it's not too bad." But don't be harsh. And when you see improvements, do tell him. Keeping it honest will help your complements get through to him, and he'll value it more. But don't ever be rough or mocking. Even if you are just joking.

My wife used to be like that. She's still insecure about her looks, but at least now, when I complement her, it does make her happy.