Present simple negatives; negative contractions;& negative interrogative forms:
I am not - I'm not / amn't I? OR am I not? OR the widely used yet very grammatically suspect aren't I?
you are not - you're not - you aren't / aren't you? OR are you not?
he/she/it is not - he's not - he isn't / isn't he? OR is he not?
we are not - we're not - we aren't / aren't we? OR are we not?
you are not - see 2nd pers. sing.
they are not - they're not - they aren't /aren't they? OR are they not?
You see "amn't I" is correct!
And I base that not only on the written word of grammar that can be seen in all verb tables, but on the fact that it is standard amongst most Irish speakers and amongst many of Irish descent; myself included. My parents used it and I grew up using it.
And also on the fact that when I went to school in Chelsea, London my English teacher used it, and often got asked by non-Irish Catholic pupils in the classroom, "Isn't that wrong miss?" whereby she would point out that amn't I is a perfectly accepted form and is in fact more grammatically correct than aren't I.
Food for thought!