Could wedding bells soon ring for Kourtney Kardashian and Scott Disick? If Disick has his way, that answer is yes.

Confronting his pregnant girlfriend of five years, 33, over her hesitation to get married during a family trip to the Dominican Republic on Sunday's Keeping Up With the Kardashians, Disick, 28, argues that Kardashian "broke the deal" the couple had about walking down the aisle.

"The whole reason I had another kid with you is because you agreed to get married," Disick reminded Kardashian, who will soon give Mason, 2, a sister when the couple's baby girl is born this summer. "You broke the contract -- you broke the deal."

Admittedly hesitant to walk down the aisle -- largely due to seeing her own parents, Kris Jenner and the late Robert Kardashian, Sr. divorce in 1991 -- Kardashian insists that she's as committed to Disick as ever, with or without a marriage license.

"I know that I'm indecisive but I'm not indecisive with you. I'm obviously committed to us, even though we're not getting married, and I thought that that was understood," she tells him in the above preview from Keeping Up With the Kardashians.

As their family continues to grow, Kardashian credits couples therapy with strengthening her bond with Disick. "He's grown so much over the years…I love seeing him as a dad -- he's great with Mason -- and I'm not saying that we're perfect," she recently told Oprah Winfrey. "We go to therapy, which helps us a lot. I think we're always working to better ourselves, which I think a lot of people can do."

Keeping Up With the Kardashians airs Sunday at 10 p.m. (EST) on E!