I'm afraid I can't give you Spanish equivalents, but "ain't" can be used to mean "am not", "is not" or "are not", and is used in the same ways as these phrases. It is quite a "stigmatized" form of English, meaning that you may sound quite uneducated if you use it. It would not be used in written language. I am not happy --> I ain't happy. I am not British --> I ain't British I am not going to do it --> I ain't going to do it. I am not eating my lunch --> I ain't eating my lunch.

Hola Ruby, ¿Cómo estás? Según la definición del Cambridge Dictionary, ain´t: (informal/slang) a non-standard or humorous way of saying or writing ’am not’, ’is not’, ’are not’, or ’have not’. En español lo traduciríamos como 'no', 'no es' o algo así en negativo. Ejemplo: ‘Can I have a cigarette?’ ‘I ain’t got none left.’ / ¿Tienes un cigarrillo? No me queda ninguno. Espero que te ayude. Saludos, Marta