Guys react to what girls say about anything. Guys are used to being hurtful around each other and then they all get laughs out of it, so to him it is fine to say your ugly looking because he's used to just laughing it off. Also he may be trying to flirt with you. Sometimes guy's say mean things but not to be mean because to them it isnt mean, they said it to flirt with you. So youll say stop it or like play slap him or something. He doesnt mean it any harm when he says it so lighten up but still if he says it more than just every now and then tell him how you feel about it. If he thought you were actually ugly he wouldnt be dating you babe.
break up with him, obviously he can't respect you. There is always some truth to a joke in my opinion. Don't take his crap anymore.
stop being so sensitive
If you've told him that it hurts your feelings and he still won't stop then it's not a joke anymore. He is purposely trying to annoy you. It's immature and you don't deserve to be treated this way. I would just break up. You sound pretty young, you shouldn't waste time on guys who hurt your feelings.