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.

A friend of the couple told Us Weekly magazine: ''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.''

But LeAnn has surprisingly gained support from Brandi - who 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.

Brandi - who has two sons, Mason, nine, and five-year-old Jake, with Eddie - said: ''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.''