I'm shy and I like to drink for courage, but does that mean I am an alcoholic?

Possibly. Drinking to make a negative feeling better is definitly a risk for a future drinking problem. Is your drinking at times uncontrolled, i.e. Do you sometimes drink more than you intended. Have bad things happened to you from drinking, fights, arguments, driving impaired, blackouts, missed other obligations. These are some questions you need to ask yourself. Be careful. Talk to your doctor about this.
Alcohol problems. Occur on a continuum. Alcoholism or alcohol dependence is at the extreme end. You can have serious problems from alcohol without being "alcoholic." the more important issue is that drinking is not the best solution for social courage. Talk to a mental health professional for better ways to resolve your shyness with far less risk than alcohol provides.