Hey Polly. I have wicked IBS and hate to admit it but I have gone as long as 11 days without having a bowel movement. I would not reccomend it! When I finally did get into the doctor for it he was none to happy with me because as Zephir said, it can be an indication of an intestinal blockage. And yes, those can be life threatening. Intestinal blockage can lead to tissue death and/or intestinal rupture which are usually fatal.
I don't know you background but I think sometimes those of us who have chronic bowel issues become so used to things not working that we forget how serious things are/can be. Get to doctor!! :)
Take care.
Polly you should not have let this go so long. You could have a blockage. Please see someone right away. I would not wait any longer. I do not want to scare you but something like this can rupture. Go 8 days is too long