"I think just with her moving on so quick, I just have a tough time understanding why she would be putting this out everywhere or blasting it all over the place knowing that it could hurt," Booth tells Higgins and Iaconetti, according to E! News. "... Her new relationship, too, just kind of makes me question everything that we've had, so I think that's one of the major questions that runs through my mind -- just trying to understand that, which I think is tough to understand, so I ask myself those questions."
The hardest part of everything, Booth says, was feeling "like everything is just completely gone, like that Kaitlyn and Shawn [are] gone."
"Not only were we engaged, but it's like, man, I lost my best friend, too," he says. "... Everything we've had, everything we've been through -- we were this team and we got through a lot of stuff together, but then just like in an instant it's all gone, so it's just trying to move on from that and then stay positive about it and not let the outside noise take you down too much."
"Because living in a world where everything is on social media, you know it's nerve-wracking every time I pick up my phone," Booth continues. "I haven't been on Twitter in months just 'cause I don't want to scroll the mentions and then going on Instagram, I do that for business purposes -- obviously get caught with scrolling and that's always tough because, you know, you have a pit in your stomach."
As for why he and Bristowe split at all, Booth admits that "we had a tough go right out the gates."
"I think everybody knows that it was a pretty dramatic season, probably one of the more dramatic seasons, but I'm not gonna lie and sugarcoat it and say, 'Yeah, it was all roses right out the gates,'" Booth says of Bristowe's season, which featured a dramatic love triangle between Booth, Bristowe and runner-up Nick Viall, whom Bristowe infamously slept with on the show before the fantasy suite dates.
"I think we started having a tough time with our relationship in, like, the second week of the season. We went through all different types of ups and downs," he reveals. "There was always push and pull, push and pull, like we were going through some serious stuff on the show and then obviously once we're engaged, we're able to announce that we're together, we're happy, we're excited and then still have to deal with other issues. I had a tough time on that show. It was always a battle of my heart versus my brain."
"I think the whole Nick situation was a big part of our relationship," he adds. "I think it's always something that was in the back of my mind. It was tough."
Following the split, a source told ET that their breakup was "just a matter of them growing apart" and said that they still "care about each other."
In a June interview with ET, Booth said that making their relationship work was "tough" at times, and said he "can understand why couples break up."
"If you're not strong enough to handle a lot of the outside noise and just the concept in general, it's very easy to call it quits," he said at the time. "We've obviously had a lot of bad times, but a lot of good times. We've just stayed humble through it all, put each other first and worked on our relationship. But it's not easy."
Despite his hurt feelings, Booth says that he still cares for Bristowe and is glad to see her happy.
"There's a part of me that... I do care about her, so I am happy that she doesn't have to really, I guess, deal with... all the pain and the heartbreak because it seems like she's moved on and she's happy," he says on the podcast. "So that's gonna make me a little more comfortable, knowing that she's not at home at her empty house. So I look at it from that point of view."
"I also think that it's helping me to move on because it does hurt that much seeing everything," he continues. "It does upset me and it does make me a little angry, but it also helps me to move on knowing that maybe we weren't right for each other."
"I will find somebody down the road that will also make me happy," he adds.
Watch the video below for more on Bristowe and Tartick's relationship: