HILARY DUFF was “making some real progress”, but she suddenly hit a wall — NOW she needs help!

The former “Lizzie McGuire” star, who’s just 5-foot-2, saw her weight rocket from a svelte 110 pounds to a chunky 145 during her pregnancy with son Luca Cruz.

Although she’s lost about 10 pounds since the baby was born on March 20, she hit a plateau. And when her efforts to get her former pro hockey-playing husband Mike Comrie to lose weight with her fell short, she asked her big sis – “Napoleon Dynamite” star Haylie – to help her drop “at least another 20 to 25 pounds,” according to a source.

“Hilary was making some real progress with her weight-loss strategy, but she suddenly hit a wall,” the source said. “She couldn’t count on her husband Mike because he let himself get flabby and was in no hurry to get back into shape.”

As The ENQUIRER reported in our July 23 issue, the gorgeous 24-year-old ordered pudgy Mike, 31, to train with her after the hunk put on 15 pounds of “sympathy weight” while she was pregnant.

So Hilary decided to call in the big gun – 27-year-old Haylie, who came up with a boot camp-style plan to whip her back into shape.

And the source says that Mike, who retired from hockey after enduring three hip surgeries, is thrilled that the pressure is off him.

“Hilary wasn’t going to wait around for Mike,” said the source. “She feels that since she’s the main breadwinner in the family now, it’s time to get her figure back for the sake of her career.

“While Mike is sitting on the couch at home watching ESPN, she’s out sweating her butt off with Haylie.

“Hilary even joked that once she’s at her ideal weight, she’s going to get Haylie to train Mike!”