Hang on. That sounds perfectly normal to me. It's a big step and it seems bigger as you get closer.
Take some time to remember why you made the decision to have the surgery in the first place. Picture your goals, grab someone you love and hold them tight.
You can also check with your surgery center. They likely have resources to refer you to a psychologist. A session or two with a trained counselor can help you sort through your feelings and regain some control.