"This is something that Scott has struggled with for years, and something Kourtney has dealt with since she has known Scott," the source explains. "When Scott starts partying, he can't stop. There is no middle ground for Scott -- it's go all in or none at all. This is how he has always been."
The source claims Disick, who shares three children, Mason, 7, Penelope, 4, and Reign, 2, with Kardashian, "goes into the dark, depressed stages" where he "turns to partying for help."
"Kourtney has had enough and does not want him around the kids until he can figure his own problems out," the source reveals, adding that the brunette beauty knows Disick is "a good father and never wanted to punish the kids with not seeing their father."
However, the source says, "the kids are getting older, especially Mason, where they know that something is wrong."
The source adds that "Kourtney's first priority is to protect her kids, and that's what she'll do," but that she is "worried about Scott."
"She has been through this so many times before and does love him; he's the father of her three children," the source shares. "She's worried this won't ever stop and hopes he gets the help he needs."
Disick, 34, has been making numerous headlines over the past month, and has been spotted getting cozy with various women, including Bella Thorne, Sofia Richie, Ella Ross, and his former flame, Chloe Bartoli, all within days apart from each other while vacationing in France for his birthday.
"Scott and Chloe have been friends for years," the source tells ET. "They have mutual friends and both love to party. They hook up whenever they are in the same place. It's nothing more than that."
His most recent Instagram snap (a solo shot!) was posted on Saturday, simply captioned, "Cruising," but photographers spotted Lord Disick arriving home from his trip at the Los Angeles International Airport on Friday.
Meanwhile, Kardashian has seemingly struck up a new romance with Algerian model Younes Bendjima. When asked if this rumored fling had anything to do with sending Disick into another spiral, the source says, "It could be."
"Scott knows that Kourtney will never take him back until he stops drinking and grows up, but it's hard for him to do that," the source explains. "Scott seeing Kourtney spending so much time with Younes definitely makes all of his own demons a lot worse."