You're afraid because it's unknown, it sounds icky and you've heard horror stories.
You're also afraid they'll find something which needs further exploration and you don't even want to think about what that could mean.
Your fear is perfectly normal. Allowing it to get the better of your common sense is a different story, however.
If you can't get a handle on it, then you must force yourself to do something about it. I see that you have been given several suggestions over the course of your questions. If none appeal to you, have you considered hypnosis?
I haven't tried it, but I do know people who have gotten hypnotized prior to undergoing stressful or scary situations (including those of a medical nature) and they say it has helped.