How Jay-Z doted on pregnant Beyonce

No wonder they're still crazy in love!

Sunday's MTV Video Music Awards show was an unforgettable night for Jay-Z and wife Beyonce -- who joyously confirmed her pregnancy onstage before a TV audience of millions. (Clutching her bump, the "Love on Top" singer announced that she was expecting just a couple hours before on the black carpet, with her rep confirming the news to Us as well; the Grammy winning superstar is about four months along, one source says.)

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And backstage, the first-time parents-to-be were just as pumped up. With adjacent dressing rooms (Jay-Z, 41, shared his with pal and "Watch the Throne" partner Kanye West), "Jay was doting on her the whole time," a witness tells Us Weekly.

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And the rapper-mogul (real name: Shawn Carter) even catcalled his wife of three years! Says the backstage source: "He yelled, 'Mmm hmmm, Who's that sexy lady walking down here?' playing like he was flirting with her. It was so cute."

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The "Empire State of Mind" MC was also mindful of his love's condition. "He was really taking care of her, asking her how she feels and helping her walk," the source says. "It was so sweet to see him like that."

Also taking care? Beyonce's mom, Tina Knowles. "She was on top of EVERYTHING - getting Beyonce everything she needed... Between Jay and her mom, she was totally taken care of. Her mom was getting her everything she needed."

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The superstar couple's famous friends got in on the baby joy, too.

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"Kanye looked like the proud uncle!" adds the witness. And Beyonce's "Telephone" duet partner Lady Gaga (dressed in male drag as "Jo Calderone) made frequent visits to the dressing room as well. "She kept coming over to rub Beyonce's belly and say hello," the witness explains, "And the security guards thought she was a guy at first and wouldn't let her back! It was really funny."