"A lot of it had to do with a little bit of the drinking that he was doing and I kind of didn't really appreciate it and respond well to it," Brice told The Bachelor host Chris Harrison during the couple's appearance on Monday night's broadcast of The Bachelor: The Women Tell All on ABC.
"I thought it was keeping us together!" O'Connell jokingly interjected before turning more serious and stating that he's now been sober for about two years.
"But things are going real good now and I haven't been drinking," O'Connell continued. "I haven't had a drink in almost two years or something like that."
"Two years, so amazing," Brice said as the show's studio audience applauded.
"She said it was 99% of the problem, so I'm pretty much 99% perfect in the relationship now," O'Connell added with a laugh.
The couple also explained how they reunited last fall after their break-up a year earlier. Brice said that their reunion was jump-started by, of all things, a giant Garfield costume.
"[My friends and I were] at this place in L.A. where everyone goes for Halloween, and I know that Charlie's the only person in L.A. that's gonna wear this huge Garfield outfit and I walk in and I look at my friends and I'm like 'Oh my God, I know it's him. I know it is,'" Brice told Harrison.
"And I walk up to him and I just had a brown wig on and I looked at him and I could see him [looking down at me] -- you know I'm 5-2, I'm short -- and he's like -- I don't even know what happened but we went home together that night," she added with a laugh and a shrug.
While he was noncommittal about what lay ahead for their relationship, O'Connell didn't dismiss the ideas of wedding bells or children in their future.
"We're working on our relationship, and there may be an engagement in the future, and there could be a family," O'Connell told Harrison. "That's were we stand. We stand with hoping to have the future together." "We're really best friends, and I have to say that ever since we've been back together almost a year now, our relationship has been everything I could ever imagine," Brice added. "It's been really amazing."
Brice had previously revealed that O'Connell's drinking had played a factor in the couple's break-up during an interview last fall, however O'Connell had seemed more reluctant to acknowledge his drinking's role.
"He's not drinking anymore, so that's a huge thing in our relationship," Brice said during a joint interview with O'Connell that aired on Extra.
"Maybe," O'Connell responded at the time when asked him to confirm his drinking had been one of the issues behind the couple's break-up.