Here's why:
* "Ain't" is considered nonstandard English. It's a contraction of "am not," "are not," or "is not," but it's generally avoided in formal writing and speaking.
* "Rsquot" is not a real word. It seems like a misspelling of "aren't" or "isn't."
* The sentence structure is incorrect. You can't use two negative contractions (ain't and rsquot) in a row in a sentence like this.
A grammatically correct and standard way to say this sentence would be:
* "I'm not hungry."
* "I am not hungry."
* "I'm not feeling hungry."