She screamed for her life - but he savagely stabbed her to death.

A man has confessed to nearly decapitating his 23-year-old girlfriend early this morning in a bloody knife attack after a loud argument inside their apartment at 63 Clinton St. on the Lower East Side, cops said.

Raul Barrera, 33, was charged with murder in the grisly domestic attack on gal pal Sarah Coit, 23, who was breaking up with him, cops said.

"She was yelling ‘No, no, stop, stop, don’t hurt me!’ " said Brianna Andalore, 20, who was staying with a friend in the building. "My friend who lives her told me this has been going on for awhile, they’ve been fighting like that for months. We were watching from our front window, when she was brought out. The cops were yelling, ‘Don’t look, don’t look!’ Her head was almost off, her neck was wide open."

Coit, formerly of Greenwich, Conn., shared a third-floor apartment with Barrera, neighbors said. She was stabbed repeatedly at 2:30 a.m., and 7th precinct cops found her lying in the blood-soaked living room after getting numerous 911 calls about the fight.

A police source said Barrera came to the 9th precinct after a relative he’d called told him to turn himself in.

Coit was rushed to nearby Beth Israel Hospital nearby, where she was pronounced dead.

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