IN THIS ISSUE: Kristen Shakes Her Booty for Rob

Kristen Stewart treats her boyfriend, Robert Pattinson, to passionate private dances, a source tells OK!.

OK! GALLERY: ROB & KRISTEN CATCH A CONCERT AS A COUPLE

Kristen has been practicing the art of striptease since taking lessons for her upcoming film Welcome to the Rileys. (She plays a prostitute/stripper.)

OK! VIDEO: KRISTEN STEWART'S WELCOME TO THE RILEYS TRAILER

And Twilight co-star Rob reaps the benefits!

"Kristen isn't just good, she's great with the sexy moves," says the source. "She admits to friends she feels super sexy when she gyrates to the music and struts around."

OK! VIDEO: K-STEW'S ON THE ROAD CO-STAR SAYS "SHE'S FANTASTIC"

Rob feels pretty good, too.

"Rob already thought Kris was the sexiest woman in the world," notes the source, "but the first time she offered him a lap dance, he couldn't believe his luck."

FOR MORE ON ROB & KRISTEN, PICK UP THE NEW ISSUE OF OK! IN STORES NOW!