First off, I'm proud of you for breaking up with the guy. That was a very wise move that proves that you respect yourself. When a girl stays in an abusive relationship, she's rewarding the guy's bad behavior, teaching him that it's acceptable to treat her that way. He makes her feel like she should be honored that he's willing to tolerate her. In reality, she's better than he deserves.
The reason why a guy would tear down the self-esteem of a girl is because his own self-image is so low. When a guy has low self esteem (which is often caused by emotional abuse coming from within his family), he learns to use insults as a form of emotional manipulation. He feels that the only way that you would stay with him is if your self-esteem was lower than his. So, he tears you down to keep you. As messed up as it sounds, he hurts you because he wants to be loved. It really says nothing about you, your waistline, or your intelligence. It says everything about his insecurity and own interior wounds.
You will find that praying for him will be a form of healing for you. But whatever you do, do not go back to him out of pity, in order to try to save him from his emotional problems. He needs to learn to bless instead of to curse, and the only way he'll open his eyes to this fact is if his attitude ends up costing him the friendships and love he's really looking for. Stay away from him, and learn to avoid guys like this in the future. You deserve to be honored. But you will never convince a man of your dignity unless you first convince yourself. So take a break from relationships, and deepen your relationship with God. He alone can show you your true worth, and no one will be able to shake that.