Scott Disick says it "hurts" to see his ex-girlfriend Kourtney Kardashian dating other people.
The 37-year-old reality star split from Kourtney - with whom he has Mason, 11, Penelope, eight, and Reign, six - in 2015 after a lengthy on-off romance, and since then they have both dated different people.
But Scott - who was in a relationship with Sofia Richie from 2017 until August last year, and is now dating Amelia Hamlin - has said he can't stand to see Kourtney flirting with other men.
In a sneak preview of this week's 'Keeping Up with the Kardashians' episode, Scott tells Kourtney: "I feel like it annoys me when you flirt with this lifeguard."
And when Kourtney insisted she wasn't flirting, Scott admitted he's too "insecure" to handle seeing his former flame with another man.
He added: "Then it's my insecurity that I feel like I just don't like seeing you with another guy. It hurts me when you're with somebody else.
"Waking up to, like, looking at pictures of you with this guy you were dating ... it's just unhealthy. It made me upset and sad, you know what I mean? And now I wake up with no real problems. I'm, like, carefree in a sense that I don't have that, that used to take up a lot of space in my mind all day. But the big fear is if you start dating again, then it goes back to that and I have to feel like a different way again and it's just hard. It sucks."
At the time of filming the clip, both Scott and Kourtney were single, but the Poosh founder has since begun dating Blink-182 drummer Travis Barker, whilst Scott is in a relationship with 19-year-old Amelia Hamlin.
And in the teaser, Scott admits he would love to rekindle his romance with Kourtney again, especially as they already spend so much time together because of their children.
He told her: "I guess now that you're single and I'm single and you haven't been with somebody in a bit, either we figure out creating our own lives together or separately."
Whilst in a confessional, he added: "It's definitely difficult that Kourtney and I basically spend 90 percent of our lives together, travel together, do everything together, see each other every day, and the only difference is at the end of the night we part ways and go and sleep in separate houses. This whole limbo state isn't that cool anymore. And I surely don't want us both to wake up and be 50 years old and doing the same thing."