LeAnn Rimes -- I'm NOT Anorexic or Addicted to Laxatives

LeAnn Rimes is full of crap ... but in a good way ... 'cause the singer tells TMZ she's NOT addicted to laxatives ... despite allegations made by "Real Housewife" Brandi Glanville. The gloves came off this week when Brandi (a.k.a Eddie Cibrian's…