If I'm this fat and ugly, I have no right to ask for something better

You're selling yourself short. Every woman is worth the world and that's why, when I love a woman, I try to give her nothing less. You should find a man that gives you everything.

Talk to your partner and see if he can fill the needs that aren't being met. If he still can't, maybe you need to consider that you aren't the right fit. But talking is key.