Hi fen3,
I dont think there is a suggested script. Why don't you try writing down what you want to say, and if it really is that hard, just pass the paper to the doctor. I don't think there's an easy way out of this. You just have to say it out to the doctor. For the doctor to be really able to help you a 100%, you need to be a 100% truthful.
I know its hard, but you have to pull up the courage to spit it out. You and only you know whats going on. Its just once, and you have the hope and means to get better. Isn't that so much more rewarding than to continue drinking, much much more since you already made up your mind to see the doctor.
You can do it! I have hope and I will pray for you as so will the rest of us. Best of luck and do let us know how it goes with the doctor.