hey HazelGirl,

BDD is Body Dysmorphic Disorder.

from Wikipedia:
'Body Dysmorphic Disorder is a chronic mental illness, a somatoform disorder, wherein the afflicted individual is concerned with body image, manifested as excessive concern about and preoccupation with a perceived defect of their physical appearance. An individual with BDD has perpetual negative thoughts about their appearance; in the majority of cases, an individual suffering from BDD is obsessed with a minor or imagined flaw.[1] Afflicted individuals think they have a defect in either one or several features of their body, which causes psychological and clinically significant distress or impairs occupational or social functioning'

^that's all quite wordy for me.
But i can't summarise it myself right now..
It's horrible that's all i can say.. been the bane of much of my life.