09/06/2012 11:52 am ET Updated Sep 07, 2012

Did LeAnn Rimes Enter Rehab After Fears Of Eddie Cibrian Cheating?

LeAnn Rimes shocked fans when she entered rehab to "cope with anxiety and stress" two days after her 30th birthday. Although a representative for the country singer said that she is there to learn how to cope, new rumors suggest Rimes has feared that husband Eddie Cibrian is cheating.

Rimes entered a 30-day in-patient program on Aug. 30. "LeAnn has voluntarily entered a 30 day in-patient treatment facility to cope with anxiety and stress," her rep Marcel Pariseau told People magazine. "While there will be speculation regarding her treatment, she is simply there to learn and develop coping mechanisms. While privacy isn't expected, it's certainly appreciated."

But Rimes' stress may be related to Cibrian.

"LeAnn has had major insecurity issues since she first got together with Eddie," a friend of the couple told Us Weekly. "She's been stressed about always being called a home-wrecker and also worried that Eddie is cheating on her. She's been on a downward spiral."

The 30-year-old singer met Cibrian while filming the Lifetime movie "Northern Lights." The two engaged in a steamy affair in 2009, cozying up at restaurants and meeting for trysts at hotels. Both were married at the time -- Rimes to former backup dancer Dean Sheremet and Cibrian to model Brandi Glanville. The couple eventually went public with their romance, got engaged and married in a private ceremony last April.

Cocktail waitress Scheana Marie told "Access Hollywood" that she and Cibrian had an affair that began in 2006 and continued until around the time Cibrian began seeing Rimes.

Since getting involved with Cibrian, Rimes has had to deal with cyberbullying targeting the 2009 extramarital affair, Us Weekly reports.

She has also had to face harsh words from Cibrian's ex-wife. "He will be with her until he cheats again. They won't be together forever. I'm totally over Eddie," Glanville previously told HuffPost's Naughty But Nice Rob.

However, a friend of Rimes says that the singer is doing just fine. "She's already feeling better, stronger," a friend of the country star told People.

"I'm happy and healthy. I just want to be happier and healthier more consistently," Rimes told People prior to checking into rehab. "I don't want to wake up and not truly be enjoying my life and these amazing things around me."