LeAnn Rimes is "worried" husband Eddie Cibrian is cheating on her.

The "Can't Fight the Moonlight" hitmaker - who checked into rehab to deal with "anxiety and stress" late last month, one day after her 30th birthday - has reportedly got
"major insecurity issues" and is feeling "stressed" about still being branded a home-wrecker for embarking on a relationship with Eddie in 2009 while she was married to chef Dean Sheremet and he was wed to Brandi Glanville.

"LeAnn has had major insecurity issues since she first got together with Eddie. 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," a friend of the couple told Us Weekly.

But LeAnn has surprisingly gained support from Brandi - whom Eddie eventually left to be with the 30-year-old singer in 2009 after they met on the set of TV movie Northern Lights - who hopes her former love rival finds "what she is looking for" in the 30-day in-patient facility.

"I totally support LeAnn's decision to enter rehab - my top priority is my children, and at the end of the day we are a family. LeAnn is their stepmom, and they love her. I am wishing her all the best and I hope she will find what she is looking for while in rehab," said Brandi, who has two sons, Mason, nine, and five-year-old Jake, with Eddie.