Liz, i'm sorry i'm going to be really bossy and hard but you really do not have a choice. Do you really want to risk your life over some embarassment? if not just for yourself do it for those that love you.
I am sure that if you explain the situation then you will be able to get some kind of sedation to help you through. Maybe your GP can prescribe you something to get you through it.
Now please go and do it and whatever the results your family and friends and us can help you deal with the results