Penis Dysmorphia is a very real mental disorder. Just as Body Dysmorphia affects the way we see our body, penis dysmorphia changes the reality of how we perceive our penis. Men who have this condition view their penis as abnormally small to the point of shame, humiliation, and isolation. They generally avoid all sexual activity due to these feelings.
While it is perfectly normal for a guy to wonder how he measures up to other guys, this condition goes far beyond that. No amount of proof, evidence, or facts will change their belief that their penis is freakishly small. Even when sex partners told him he was bigger than average, he did not believe them. It took several years of therapy and anti-anxiety meds to recover from this belief.