On-and-off couple Shanna Moakler and Travis Barker are off again – but this time, a source insists, it's for good.

"About a month ago, they separated again," the source close to Moakler tells PEOPLE. "She moved out. As far as she's concerned, it's over. She loves him, but it's one of those relationships where they keep trying to make it work but it doesn't."

Moakler, the source says, is taking the split hard: "She's very upset. She gave this marriage her all. She really loves him."

No reason was given for the split. Barker's rep didn't immediately respond for comment.

Moakler, 32, a former Miss USA who appeared on Dancing with the Stars,' and Barker, 31, who played drums in blink-182, had a bitter breakup last summer, with Barker filing for divorce, but got back together in March.

Before their split, the pair appeared in their own MTV reality show, Meet the Barkers. They have two children together, Alabama Louella, 1, and Landon, 3. Moakler also has a 8-year-old daughter with boxer Oscar De La Hoya.

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I didn't even know they had gotten back together......