You are an alcoholic (A) if you are having negative consequences from your drinking (psychal, mental, spiritual, family/friends/work etc) and (B) if you ever feel like you can't control yourself. Like you just can't say no.
Do you think about drinking a lot when you aren't? Do you feel like you need to be drunk to have fun or feel "right"?
Have you a pattern of putting alcohol first, at the expense of other priorities in your life? Remember that there can be different degrees of severity, but chances are that if you have to ask, then you already sense the answer. Ever heard of Alcoholics Anonymous? Perhaps you should go to a meeting (they're open to most anyone, even if you're not quite sure if you really need to be there) and see what the others have to share about their experiences and if you see any parallels, and they have a little pamphlet called "am I an alcoholic" (as well as some other neat little pamphlets) that might help you out.
Well now that I've taken up so much space, I'll end with saying that only you can determine if you are and how you feel about it.
BTW, That's a lot of f-ing alcohol you had on Thursday!