I had an endoscopy when I was 13/14. Was terrified about being put under anesthesia. You honestly don't have anything to be worried about. A good half hour before my endoscopy they set me up with an IV filled with some pretty mellowing drugs. All the anxiety and fear just melted away into relaxation. It felt like a few seconds had passed when I came to but it had apparently been a few hours after the endoscopy. Simply put the Doctor will make sure you are extremely comfortable from beginning to end.