The couple, who divorced in 2004 but reconciled last September after Barker's near-fatal plane crash, called it quits "after a nasty fight broke out at his house last night and cops were called ... [when] Shanna started freaking out and acting irrational," the source continues.
No charges were filed.
"Travis confronted Shanna about her having an affair with Gerard Butler while he was in the hospital recovering," the source says. Butler and Moakler were spotted getting cozy at the Hollywood opening of Shin Korean BBQ last October.
Barker "just wants to focus on his music and his children right now. He is done with her drama," the source says.
In February, Barker told Us he "couldn't be happier" after reuniting with Moakler, who was spotted wearing her wedding band at a Grammys party.
Barker's rep tells Us exclusively, "After surviving the plane crash his driving force in life is the love he has for his kids. He is tired of all other drama and is ready to move on."
A rep for Moakler tells Us: "They did break up but Shanna never cheated on Travis while he was in the hospital. Furthermore, Shanna is tired of playing out their personal relationship in the press."
Barker, 33, and Moakler, 34, are parents to Landon Asher and Alabama Luella. She also has a daughter, Atiana Cecilia, with ex Oscar de la Hoya. They starred in the MTV reality show "Meet the Barkers" in 2006.
"The babies are the most important thing right now," adds the insider. "Shanna cheated on him and then told everyone they were in love again while she was having an affair and he was recovering from the accident."
Barker spent a month in the hospital with second- and third degree-burns on his hands and lower body following the crash, which killed four people and badly injured Adam "DJ AM" Goldstein.
"It's over now and he just wants to move on," the pal says.