"We don't live together," Pratt tells PEOPLE, shooting down a report that they're cohabitating even though Montag filed for divorce last week.
Pratt, 26, has been in and out of the couple's Pacific Palisades residence, while Montag, 23, is living in Malibu.
Still, Pratt and Montag do see each other often.
"Spencer and I are finally moving forward with our lives, but with any divorce there is much to work through," Montag tells PEOPLE. "We've been together almost five years – there are assets to divide, work to be discussed, and we share our puppies."
The split hasn't been easy on either one. "This has been a heartbreaking experience to go through and it's not that I don't love Spencer," Montag explains. "We just want different things in life."
Pratt also says he loves Heidi – but calls their marriage a show.