Scott Disick is rumored to have hooked up with one of Kourtney Kardashian's best friends, putting his hopes of reconciling with the mother of his three young children in grave danger.

Us magazine reports Disick is now regretting his dalliances with Kimberly Stewart, 36, and feeling like an "*sshole."

A source added, "He was trying to get Kourtney back and was hoping she didn't find out." Though reports are the two had "multiple romps," Stewart, who now stars on her family's E! reality show "Stewarts & Hamiltons," continues to deny the affair.

Earlier this week, Disick was spied having lunch with Stewart's brother Sean at a Beverly Hills restaurant, proving he that he has grown closer to the entire Stewart family. As far back as 2006, rumors about Disick and Stewart circulated, when he was spotted with his arm around her backstage at a New York City fashion show.

The daughter of rock legend Rod Stewart, the leggy blonde has a 4-year-old daughter with actor Benicio del Toro.

Meanwhile, reports are that Disick is also dating 22-year-old model Makayla Yarbrough.

"They met during one of Scott's Las Vegas appearances a few weeks ago, and they've been partying together ever since," said a source.

Rumors are Yarbrough has been spending time at Disick's LA pad and bragging to friends of sleeping with him.

"Kourtney still has no interest in getting back with him," said a source.

"At the end of the day, he wants to get back together with Kourtney," added yet another source. "That's his ultimate goal. He wants his family back together."

The two split earlier this year after Disick spent the July Fourth holiday weekend cavorting abroad with former girlfriend Chloe Bartoli.