I'd say it depends on the person and isn't realted that much to Crohn's. The normal "healthy" frequency of bowel movements (as doctors lovely call them...) is 1-2 per day. Specifically during travel I had 3 days on a row where I just could not go. It is not comfortable... I'd say if you go beyond 3 days and feel rather uncomfortable, may mean that calling up your doc makes sense. How many days have you not been able to go? Also, are you in pain? If you are, definitely call up your doc.