Khloé Kardashian Odom Filing for Divorce From Lamar Odom "Later Today"

E! star tried continuously to help husband end his substance abuse throughout the past several months

After four years of marriage, Khloé Kardashian Odom and Lamar Odom are calling it quits.

A source confirmed to E! News Friday, Dec. 13, that the 29-year-old plans to file for divorce "later today."

The decision to call it quits was undoubtedly difficult for the Keeping Up With the Kardashians star, who had been instrumental in trying to help Lamar put an end to his substance abuse problems. Through early November, she and Lamar, 34, were continuing couples therapy, a source told E! News exclusively, adding that the pair was "using it as a forum to talk through all of their issues."

"Khloé has been very, very hurt by everything," the source added. "There is a lot about Lamar that she is just learning and if they have any chance of making this work, there is a lot they need to come to terms with."

Weeks later, Lamar chose to spend Thanksgiving with his father, Joe, instead of his wife. Just two months prior to the holiday, however, Lamar slammed his dad for "disrespecting the ONLY FAMILY [the Kardashians and Jenners] that has loved me without expecting anything in return."

Khloé had given Lamar "an ultimatum" in September, following his one-day rehab stint and DUI arrest, telling him "if he didn't get help, she'd end the marriage." (On Dec. 9, Lamar entered a no contest plea for his run-in with the law and was sentenced to 36 months of probation.)

But it seems that Khloé finally reached her breaking point. Fortunately, though, it seems like she's learned from this struggle and is staying strong. Just one day before she took the first official step towards ending the marriage, she posted an insightful, telling quote on Instagram that read: "I am strong because I've been weak. I am fearless because I've been afraid. I am wise because I've been foolish."

Khloé and Lamar tied the knot on Sept. 27, 2009, at a private Beverly Hills estate after a whirlwind courtship.

They met when Lamar was still playing for the L.A. Lakers, then moved briefly to Dallas for the 2011-12 NBA season while he played with the Mavericks. They resettled back in L.A. full-time when Lamar joined the Clippers last year.

Although Lamar has not officially signed on for another season with the team, he's been training in Rhode Island, and his "plan is to get back and sign up with the [Los Angeles] Clippers."