Charlie Sheen's ex-wife Brooke Mueller has checked back into rehab, reports from People Magazine and Us Weekly have confirmed. Mueller, who has struggled with substance abuse in the past, has reportedly signed up to particulate in a six-month-long treatment program. 

Mueller has already spent a month-and-a-half at the facility, a source confirmed to the publications. There are no reports suggesting why the 38-year-old has decided to seek treatment; however Mueller was reportedly seeking treatment for addiction issues.

This is reportedly Mueller's 20th stint in rehab, the Daily Mail noted. She previously entered treatment facilities in 2010 and 2012 In December 2011, Mueller entered into a "long-term, in-patient treatment center" for substance abuse following her arrest for assault and alleged cocaine possession. RadarOnline claimed in 2013 that Mueller secretly went to rehab twice while pregnant.

"She went to rehab twice because she was using drugs," a source said. "It just shows how far gone Brooke is with her battle of using crystal meth. The fact that she couldn't stay sober while carrying Bob and Max caused Charlie great anguish."

Mueller's rehab news comes two months after her ex-husband, Sheen, announced that he is HIV positive. Following his announcement, Muller, who shares 6-year-old twins Max and Bob with Sheen, revealed that neither she nor her son had contacted the disease.

"Brooke has been inundated with calls from friends and family," Mueller's rep, Steve Honig, said in a statement, according to Entertainment Tonight. "To put their minds at ease, Brooke can confirm that she and the boys are not HIV-positive."

Sheen told RadarOnline that Mueller had been supportive of his HIV diagnosis, saying, "She was sad for me but then realized that I'm a pretty tough customer and she knew I would handle it and do whatever I had to."

Sheen and Mueller were married from 2008 to 2011.