1) Flush the toilet before using it to check its working.
2) Change your diet (make it healthier if it is not healthy). Diet will influence the nature of your stool which in turn will determine the outcome of the toilet (whether its clogged or not)
For treating your phobia, the following physical changes should help: diet, exercise, yoga.
To change your phobia psychologically, I think that you are holding on to the embarrassed feeling from the wedding incident you mentioned. <-- My apologies if I am wrong for assuming this but I have some embarrassed memories that have scarred me and sort of created a phobia. The way I dealt with it was through forgiving myself and moving on.
Good luck