MARIAH CAREY WAS ACTING REAL FUNNY DUDDY & NICK CANNON'S 30TH BIRTHDAY PARTY!

Maybe Mariah Carey should have called her last album "Memoirs of An Imperfect Diva."
The sexy songbird didn't exactly quash pesky pregnancy rumors or her reputation as high maintenance at husband Nick Cannon's 30th birthday dinner at Lavo NYC on Friday night.

Melismatic Mariah kept her goods under cover for much of the night. Upon arriving, she refused to pose for pictures outside the club and insisted on entering Lavo through the back door.

Once inside, she spent much of the evening shrouded in a black trench coat, and only after the festivities were well underway was she coaxed into taking a few photos.

First, however, Carey insisted on freshening up. According to a source who was on hand to help Cannon celebrate, this entailed a small special-ops "team of stylists and makeup artists" accompanying Carey into the bathroom, where they "re-did" the singer.

Properly primped, Carey shed her coat to reveal an unusually baggy, short, black frock that showed off her fishnet-stocking-clad gams but camouflaged what our source says was a suspiciously protruding tummy. And not long after the approved shots were snapped, Carey re-donned her rain gear.

Weirdly, given her choice of outerwear, our source says it was Carey who put a bit of a damper on the festivities. While Cannon made the rounds, chatting with R&B artist Ne-Yo, "SNL" cast member Jay Pharoah and BET Executive Vice President Stephen Hill, "Mariah wasn't really mingling," our source observes. Instead, she sat in the same place "practically the whole night."

The 40-year-old Carey didn't even try Cannon's birthday cake, which took the form of a large No. 30. And, despite her reported love of Champagne, she stuck strictly to cranberry cocktail juice, further fueling rumors that she's carrying Cannon's child.

The "touchy feely" couple departed directly after dinner, although not before more drama ensued.

Carey, we're told, wanted to exit as she entered - through the back door - for an unusual reason. Leaving via the front involved traversing two steps, and, our insider overheard the singer's handlers discussing that "Mariah doesn't do stairs" - perhaps because of her sparkly, skyscraper-high black heels.

When it was determined, however, that paparazzi had amassed at Lavo's rear entrance and that the front door was the most secure way to exit the building, Carey braved the two-step descent and she and Cannon made their escape.