Interesting question, first of all I don't think there's anything wrong with you, I know that when I forbid myself something (like cake when I'm trying to loose weight) I just want it more and think about it more - I made the cake the aim of a lot of my emotions concerning my body and my self perception and so, it's becoming the target of so many thoughts and emotions. so instead of thinking "I hate myself cause I'm fat" I'm thinking "I'm not allowed to ever have cake".
If your story is true and you aren't drinking more then you are telling and using this question as a way to get people to tell you you are not an alcoholic so you can drink more - here are a few facts:
1) nothing is addictive from using it once or twice it takes a while for the body to form a habit.
2) Alcohol washes out of your system (leaving the damage it did to the liver \ kidnys \ brain) in about 24 hours at most, any dependency you might have created in yourself now is emotional, not physical.
3) Though addictions are hereditary, it doesn't mean that 100% of children of addicts will also be addicts.The gene of addiction might exsist, but you'd have to combine it with other social and educational factors to become an addict.
What's making me curious and scared for you is this - you know that your mom and your grandmother both drunk themselves to death. You made the choice in your life not to drink. How come you are having bloody marries all of a sudden? what happened? you kept that out of the question and so I think that you are trying ti hide something from us and from yourself.
I think that a part of you wants to test yourself with alcohol to prove you are not like your grandmother and mother an in the course of that - you might fall into alcoholism.
I think that this is a huge issue for you and though there's nothing wrong with you physically, I think you should seek professional psychological help and learn how to deal with your feelings towared drinking and the probably horrible experience of living with n alcoholic parent.