I think I understand now what you meant when you said you were unable to hold much, and I am making the assumption that your colonics are with a gravity flow system, is that the situation? Do you know if it is a Libbe system?
But whatever it is, it sounds like your colon is fairly impacted with waste matter such that there is not much room in there for the water without causing an immediate urge to evacuate.
Did you go for a colonic as a result of constipation problems? (As I'm replying to your latest posting I can't go back to review your original one). Had you been using enemas beforehand to help clear waste matter from your colon? Do you have future colonics scheduled?
I'll go back and reread your original posting and follow up if I'm missing anything here.