How do I look better?

You do know that people close their eyes when they kiss, yes? I suspect that's partly because everyone looks weird that close up. Besides, she's obviously not repulsed by your appearance, or she wouldn't be dating you. Heck, she may be wondering how you're able to overlook what she sees as her enormous, glaring flaws. Don't overthink this and let your anxieties get in the way of what could be something great.