Carrie, no reason to lie, and no reason to tell them you are an alcoholic.
Real simple. Here is your response if you need to make one when offered an alcoholic beverage .......................
"Because of my current stomach problems. my doctor has advised that I abstain from all alcohol."
Real simple and it is the truth as alcohol aggravates the gastronic system.
There. You are not lying. You can stick with your desire not to drink and in the process, it will also shut up that 'voice' that I like to call King Alcohol.
Hope that helps.
Love and hugs,