A source confirms to PEOPLE that the country singers – who celebrated both of their best new artist nominations at the Academy of Country Music Awards in April – blame their careers for the split.
"They are both so busy right now," a source says. "They are both on the road and have to spend a lot of time apart, which isn't ideal for any couple, let alone a couple trying to plan a wedding."
Luckily, it doesn't sound like the break-up is to the sound of a typical country song.
"There was no foul play involved, it's nothing like that," the insider adds. "They were happy together but know what's best."
The former One Tree Hill starlet, 29, was previously married to Johnathon Schaech for a month in 2010, and to Michael Gambino in 2004.