Question

1. Aren't I pretty?
2. Ain't I pretty?
3. Am I not pretty?

4. I'm pretty, aren't I?
5. I'm pretty, ain't I?
6. I'm pretty, am I not?
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Are they all grammatical?

Answer 1

Only 3 and 6 are right. However, they sound awkward to many of us -- so we just avoid saying it.

We could say,
Don't you think I'm pretty?
I think I'm really pretty today.