KRISTEN STEWART needs to clean up her act – literally!  Her grungy habits and B.O. are turning tousled haired R-PATZ OFF!

The “Twilight” beauty’s body odor and disheveled appearance are starting to rub her beau Robert Pattinson the wrong way – and he’s warned her that he’ll dump her for good if she doesn’t change her slovenly ways.

“Rob’s a laid-back guy, but he is starting to find Kristen’s grungy habits a turnoff,” a source told The ENQUIRER. “She rarely washes her hair, only brushes her teeth once a day at best and very rarely wears perfume.

“He loved it when she made an effort to look her best during the ‘Twilight’ promotional tour. But now she’s back to her lazy old self, and Rob’s not impressed.”

Earlier this year, Robert was humiliated when it was revealed that Kristen had cheated on him with married “Snow White and the Huntsman” director Rupert Sanders. Although the pair have since reconciled, insiders say the relationship is fraught with tension.

“Ever since they got back together, Rob has been super-critical of Kristen,” revealed the source. “Before the whole cheating thing, she could do no wrong. Even when she didn’t shower for days, he’d tell her she smelled great. But things have changed since then.

“He’s looking at her in a different light and he’s nowhere near as forgiving as he used to be. He told her that if she doesn’t do something about her hygiene and appearance, he’s leaving.”

But it seems that Robert’s complaints are falling on deaf ears.

“Kristen is very set in her ways,” added the source. “When she’s not working she just can’t be bothered to wash her hair or put on makeup – it’s just not her.”