LeAnn Rimes Checks into Rehab -- I've Got 'Emotional Issues'

LeAnn Rimes -- the woman who put on the perpetually smiley face after being the other woman in a love triangle involving a married couple -- now says she can't cope with the stress ... and has checked into a treatment center.

A rep for Rimes ... who has spent the past year habitually tweeting out bikini photos of herself ... just released a statement to People.com saying, "LeAnn has voluntarily entered a 30-day in-patient treatment facility to cope with anxiety and stress."

"While there will be speculation regarding her treatment, she is simply there to learn and develop coping mechanisms."

Rimes also issued a statement herself ... saying, "This is just a time for me to emotionally check out for a second and take care of myself and come back in 30 days as the best 30-year-old woman I can be."