Why is my tailbone (coccyx) hurting so badly? I haven t fell or injured it, but it hurts to sit, stand, walk, even lie down. I have anorexia and been severely underweight for about two years so I m assuming it has something to do with that, but what is the actual reason it s hurting and how can I make it stop? I m a 19 y/o female, 5 6 and 90 pounds.