updated 03/28/2012 AT 12:00 PM ET
•originally published 03/28/2012 AT 1:30 PM ET
“I was very resistant,” she tells PEOPLE in an exclusive new interview. “I didn’t want it to happen. It took me some time to come to peace with it.”
The couple, who wed in 2001, always had what looked like a storybook marriage. Parents to daughters Luca, 14, Lola, 9 and Fiona, 5, they dubbed themselves the Facinelli Five and reveled in family traditions that included camping in an RV, family movie nights and bingo tournaments.
But over the past two years, as Facinelli’s career was taking off (he plays Dr. Carlisle Cullen in the Twilight series and is a regular on Showtime’s Nurse Jackie), the couple began spending more time apart.
In 2010, Garth, 39, and their daughters moved to the family’s Santa Ynez Valley, Calif., ranch house, while Facinelli, 38, commuted from Vancouver and New York City.
“He would do everything he could to fly back every weekend,” says Garth. “[But] it took a real toll on our marriage.”
Since then, “I’ve gone through my darkest parts and I’m coming out of it,” says Garth, whose new CMT reality show, Jennie Garth: A Little Bit Country, premieres on April 20. “I’m okay. I don’t know what the future holds, but then I’ve never been a planner. And maybe that’s a good thing.”
For more on Jennie Garth’s life as a single mother, pick up the latest issue of PEOPLE, on newsstands Friday