Kourtney, the eldest of the "Keeping Up With the Kardashians" sisters, confirmed the news to Ryan Seacrest on his "On-Air With Ryan Seacrest" radio show on Thursday morning. She said she reconnected with her ex while she was in Miami filming her new reality show for E!, "Kourtney and Khloe Take Miami."
"We went to Miami to have this crazy single sister time… and then this all went down," Kourtney, 30, told Ryan. "Scott came to town and we had some time together and it was just so crazy."
While Kourtney previously told E! fans would have to watch the show to see if she and Scott got back together, she hinted the two are back on.
"He was actually excited," Kourtney said about Scott's reaction to the pregnancy news, noting he mentioned marriage. "I think he has moments where he's really scared, but he was way more excited than I was."
Though Scott was enthusiastic, Kourtney said she was nervous — at least when it came time to tell her family. She had Khloe, 25, break the news. And after hearing it, Kourtney's stepfather, Bruce Jenner, told her and Scott to get serious.
"Bruce was the most realistic. He was like, 'You guys are acting like you're getting a puppy dog. You're not. It changes your life.'" Kourtney recounted.
When asked if sister Kim, 28, was jealous over her news, Kourtney said her younger sibling was enthusiastic, but cautious.
"She was excited, but I think that she wanted to make sure I thought it through in the beginning – her and my mom… Khloe was so excited," Kourtney said. "[Kim] definitely thought it was going to be her [getting pregnant] first. Trust me."
Kourtney revealed that she's experienced nausea throughout her pregnancy. But she's also grown and not just in belly size.
"They're huge," she said of her breasts. "And they're like, so sore."
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PLAY IT NOW: Kourtney Kardashian Talks Taking 'Miami' (July 11, 2009)