... this according to his wife Kristin Cavallari who says the ex-NFL quarterback helped to unclog her milk ducts by "sucking harder than he’s ever sucked."

K-Cav made the statement on camera for an upcoming episode of "Very Cavallari" -- when she was telling a dinner table full of friends how she solved a major breastfeeding issue.

"Major clogged ducts. Jay had to get them out for me, sucking harder than he’s ever sucked ... and you know what? Saved my life."

Jay just cracked a smile and threw up his hands as if to say, "Yeah, so what?!"

Cavallari has really introduced the public to a side of Jay nobody really knew during his 12 seasons in the NFL -- when he had a reputation for being boring, introverted and the opposite of fun.

Now, he's posing naked on the beach, blossoming into a legit reality star ... and unclogging milk ducts with his face.

CUTLER!!!