I use "ain't" quite a lot, despite sounding like a posh southern fairy (I'm from the UK).
Interestingly, for the OP, I live on the border between two counties one of which has a more rural accent where "ain't" is pronounced "eh-nt" rather than "ay-nt", so there's some variation on the language used here.
I also found myself using "ain't" more when I moved to Coventry (in the midlands) and adopted it as an attempt to emulate the colloquial dialect.
I would say "I try to use the best possible English", but I'm aware of how bloody rubbish my sentence structure is. I apologise to all punctuation and grammar Nazis for my awful writing.