Rob Kardashian More Confident With Dancing with the Stars

After Rob danced the jive on Monday ... Carrie Ann said, "It's official. Rob Kardashian is a better dancer than Kim Kardashian!"

Now sources close to the show tell us Rob is hitting the gym daily, practicing harder than ever -- and sucking up to his partner/teacher Cheryl Burke by bringing her lunch each day.

Rob's new attitude is a 180 from a few weeks ago -- when he was a total slacker.