Stop obsessing. It is simply a matter of checking in to hospital/clinic and is painless except for the IV that you probably will have. That is only a needle stick no worse than stabbing yourself with a sewing needle. Find something else to occupy your time and totally forget about the procedure. Nothing to be afraid of. Unless you doctor has said you have a specific need for colonoscopy it is only a routine screening to be sure nothing abnormal is present. That does not mean you have anything abnormal. Just making sure you don't. Once it is over you'll forget what it was that worried you so much and will say it was a breeze.
The worst part of the whole thing will be at home~~ the physic. No worse than a bad case of diarrhea. To help make it easier on yourself change your diet about a week before to include a lot of fruit and roughage. Skip things like cheese, bananas, and chocolate that can be constipating. The day before you begin process eat a very light diet with lots of liquids. The less there is to purge the easier it will be. Do not plan to go far from home as you will need frequent trips to the head. Thats it in a nut shell.
The doctor can give you something for your anxiety if you just ask. In your case you probably would do well to have an anti-anxiety drug.
GOOD LUCK; BE BRAVE!
P.S. You can have anti-anxiety drug in IV if your doctor orders it before the actual procedure begins.
