"It's been very chilly between them for a long time," an insider told PEOPLE. "They have been through the wringer before, but they've always gotten out of it."
"Tori still has major trust issues. Part of their relationship was never fully repaired after he was unfaithful," the source said of the 55-year-old actor's cheating scandal in 2014. "They've been living separate lives. They will still have family meals and occasional outings, but it's for the kids."
The Beverly Hills, 90210 alum is "determined to come out of whatever happens on top," the source spilled. "She's working really hard and has her hands in a lot of things."
Another insider told the publication that things between the couple have been "bad for a really long time, over a year for sure." The source noted that the blonde beauty does not want to break up the family because she "thinks the kids need their dad. These are their fundamental years and they've fought to stay together for the kids."
"Dean has a really, really good bond with the kids. He's been a stabilizing force for them," the source added.
"It's true he has been in Canada filming," a third source told PEOPLE. "But [for Tori] being alone with five kids and expected to handle all the day-to-day responsibilities that come along with that really took a big toll on their relationship."
The couple have been making headlines in recent months throughout their reported relationship woes. In June, Spelling shocked listeners when she revealed that she and her husband were sleeping in different beds during an appearance on Jeff Lewis Live.
Earlier this month, an OK! insider said that the pair's relationship only lasted this long because of their children. Spelling and McDermott tied the knot in 2006 and share children Liam, 14, Stella, 13, Hattie, 9, Finn, 8, and Beau, 4.
The Scary Movie 2 star "has been miserable for ages, but didn’t have the fortitude to leave," according to the OK! insider. However, when her husband traveled to Canada to work on a project, she had the time to reflect on their relationship.
"During this time apart, she realized she’s a lot stronger than she gives herself credit for," the insider explained. "She learned to make decisions for herself and to love herself again."