"Scott is like on a crazy bender," Kourtney confessed in the promo released by E!.
Kourtney's mother Kris Jenner was then shown looking at photos in a magazine of Disick, 32, getting cozy with his ex-girlfriend Chloe Bartoli, 25, during a July vacation with his buddies in Monte Carlo.
"What a piece of sh-t!" griped Jenner, 59.
Kourtney, who reportedly broke up with Disick after observing the scandalous photos, confided in her younger sister Kim Kardashian in the clip, bursting into tears and lamenting, "I worked so hard to keep this family together."
Several hours later, Disick posted a strange photo of himself that dates back to an earlier season of the Kardashians' reality show. The self-declared "lord" was sipping tea in the photo and demanded, "Stop talking, peasant."
Disick captioned the Instagram image, "Just stop."
Kourtney received a lot of support from fans on social media after the video clip of her crying circulated. She wrote on Twitter Tuesday night, "Being alone & actually sitting with our own thoughts can lead to such growth and realizations that are rare in our everyday busy lives."
Kourtney and Disick were romantically involved for about nine years although they experienced a tumultuous on-again, off-again relationship. They have three children together -- Mason, 5, Penelope, 3, and Reign, 9 months.
Sources told People recently that Disick continues to party and behave recklessly despite Kourtney's heartbreak.
"He doesn't have anyone to keep him in check. He's not interested in accountability. He's just going wild. A lot of people are trying to help him but that's not what he's looking for right now," an insider told People.
"He isn't working on himself, which is one of the conditions he has to meet for Kourtney to take him back," a source close to Disick said. "He's not working on himself at all. He's totally lost right now."