My 3 year old daughter is either constipated or holding her poo and I'm not sure which one it is. She won't go for days and on occasions stands stiffed legged and goes red in the face. She insists she is trying to 'go' but I'm not convinced. When she does go it is huge and painful. A friend told me that if you pull the legs apart it becomes impossible to hold, although I'm yet to try this. How do I know if she is telling the truth or fighting to hold in the poo?