Boy Gone Wild! A Solo Scott Disick Sprays Champagne, Parties All Night In Hamptons Birthday Bash WATCH The Crazy Video

While Kourtney Kardashian's away, Scott Disick will play!

Just days after the pregnant reality star and her baby daddy got into an epic fight in their Hamptons rental home, the legendary party boy celebrated his 31st birthday in a very belated bash at 1 Oak nightclub in Southampton, New York on Saturday night.

The same day Kardashian, 35, attended a child-friendly party for niece North West's first birthday in L.A., a girlfriend-free Disick- who actually turned 31 on May 26- pulled up to the trendy Hamptons club in his Bentley with an entourage in tow after midnight.

"He started smoking cigarettes and drinking beer," Paul Micheli of DJ Prep exclusively tells RadarOnline.com. "He seemed pretty wasted."

At around 1:15 AM, Micheli adds, the self-proclaimed "Lord Disick" was presented with a crown-shaped cake as 2 Chainz' "Birthday Song" blared.

In a partygoer's video, the failed restaurateur, looking worse for wear in a stained jean shirt, sprayed champagne on his guests as women screamed.

The ruddy-faced star left with his pals around 2:30 AM.

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Though Disick and Kardashian are expecting their third child in December, the doting daddy hasn't stopped partying it up: He chugged beers at NYC club Up & Down on June 6, and "drank himself into a stupor" at Mexico's Hard Rock Hotel Riviera Maya in May, sources told Radar.

On June 9, Disick stormed out of the couple's nearly $14 million Hamptons mansion and checked into a nearby hotel after a blowout with his girlfriend of seven years.