In some dialects "ain't" is also used as a contraction of "do not", "does not", "did not", "cannot/can not", "could not", "will not", "would not" and "should not". The usage of "ain't" is a perennial subject of controversy in English.

Could I have contracted form?

Could have been usually gets contracted to could've been or even coulda' been.

What contracted form?

have = 've I've we've, you've, they've has = 's he's, she's, it's would = 'd I'd he'd, she'd, it'd we'd, you'd, they'd will = 'll I'll he'll, she'll, it'll we'll, you'll, they'll Short forms (contractions) of negatives: Page 4 don't, doesn't, haven't, etc.