Diagnostic Criteria for 302.3 Transvestic Fetishism
A. Over a period of at least 6 months, in a heterosexual male, recurrent, intense sexually arousing fantasies, sexual urges, or behaviors involving cross-dressing.
B. The fantasies, sexual urges, or behaviors cause clinically significant distress or impairment in social, occupational, or other important areas of functioning.
It's Part B that's the problem. Happy crosdressers -Good. Unhappy crosdressers - have a mental disease (according to DSM IV).
So crossdress and be happy. I do.