Control.  If it has more control over you than you have over it, it is a problem.
If you have to have it, if you crave it, if you can't stand the idea of not doing it, especially in certain moments or certain times.  If you say "I won't", then you do, you have a problem.
And even if you don't have a "problem", too much alcohol is unhealthy and will shorten your life or give you bad health. 
edit:  Sarah, I'm a recovering alcoholic.  It takes one to know one.  You are drinking like this for a reason.  So there are two issues:
1. Drinking "problem"
2. Reason why.
Even if you stop drinking, you still have #2, and you will just find something else to replace drinking in order to "deal" with #2.
Number 2 is huge.  Nobody can ignore your problems or hurt you as well as you can.   Nobody can take care of you as well as you can.   You deserve happiness, health, and love.  Make it happen.