You've already got some great advice, so I just wanted to say CONGRATS for going for the colonic!!! woo hoo! :)
The cramping is one of the reasons why I do enemas rather than colonics now - I can constantly massage my feet on a foot roller, and you wouldn't believe how much this simple massge helps the cramping. :) If you have any kind of like neck massager that you can use on your feet next time you get a colonic - if there is a next time - bring it with you and use it best you can. And massage your abdomen too, especially at the left "corner".