not sure that the colonic is gonna help at this point. but then again, we're all different.
one thing i've come across recently is 'tension myoneural syndrome'. (put it in a google search).
the main idea is that the body creates painful conditions as a way of distracting us from emotions that we feel are dangerous or unacceptable to have - i.e. unsafe.
...which kinda resonates for me with shy bowel... after all shy bowel boils down to our bodies feeling safe or unsafe. if the body feels safe, we can poo, if it feels unsafe, we lock up.
anyway, it's something i've just started looking into. i've ordered a copy of a book called the mind/body prescription. though i think there's a newer version called 'the divided mind'. (they're both by john sarno).
hope this is of some help.