Kris Humphries finally got the news from ex-GF Myla Sinnaj -- the news TMZ broke -- that's she says she's 3 months pregnant and claims he's the dad -- but sources close to Kris tell us ... he's not convinced he's he daddy.

According to our sources, Kris didn't express his doubts to Myla ... but we're told he'll take a paternity test for proof positive.

As TMZ first reported, Myla is sure Kris is the baby daddy but wants to raise the baby on her own.  But that could change, because we know Kris is making sounds he may get back together with her.

Our photogs spotted Myla yesterday, looking only mildly baby bumpy so far.