A Manhattan trust-fund kid dubbed the “Flaccid Fiend” for becoming impotent during attacks on women has been arrested again — for allegedly beating his girlfriend and nearly suffocating her.

Eric Lewenstein, 40, the son of a prominent physician and grandson of a wealthy financier, got into an argument with his 39-year-old girlfriend in their West End Avenue apartment on Jan. 28, cops said.

Lewenstein hurled his girlfriend against a wall three times and knocked her to the floor, cops said.

The ex-con then repeatedly slugged her in the stomach and covered her mouth and nose so she couldn’t breathe, sources said, while he sneered, “Do you like your teeth? Do you know what I’m capable of?”

His girlfriend called police, who arrested Lewenstein after they found two illegal weapons in his possession — a metal baton and a gravity knife, sources said.