How much would a person need to drink for alcohol to be the culprit for someone to have gynecomastia?

I agree with the others that there is no know correlation between alcohol intake and gyneomastia. It sounds, however, that you are unsure about what has caused your gynecomastia. A thorough consultation with a boarded plastic surgeon will be of great help, I think.

I am not aware of any study that indicates alcohol as the direct cause of gynecomastia. I believe the problem is the damage that alcohol can do to the liver which then can causegynecomastia (advanced cirrhosis of the liver). 

No, alcohol itself does not cause gynecomastia.  However, excessive alcohol intake over a long time can lead to liver disease (cirrhosis) and the liver disease and associated poor liver function can result in gynecomastia.For more info about gynecomastia, please refer to my website captioned below.Elliot W. Jacobs, MD, FACSNew York City