Why My Head Is Slightly Bigger On One Side?

Hi, about 4 years ago I noticed my head was slightly bigger on one side. It's the upper right side. Today however it seems more defined, and in the past two years there has been two incidents when I blacked out and fell. At the time I was dealing with Psychological problems, and bulimia so the I and the Psychiatrist attributed to that. However it's beginning to cause me discomfort. Any idea on what may be the cause?