The DSM-IV-TR breaks diagnoses down into categories. For example, Asperger's Disorder falls under Pervasive Developmental Disorders, and this in turn falls under Disorders Usually First Diagnosed in Infancy, Childhood, or Adolescence. Bipolar I Disorder, by contrast, falls under the Bipolar Disorders, and these in turn fall under the Mood Disorders. The NOS diagnoses are wastebasket diagnoses where the exact diagnostic criteria are not met, but it seems clear something's wrong. So we have PDD-NOS, Bipolar NOS, Mood Disorder NOS, Disorder of Infancy, Childhood, or Adolescence NOS, etc.
So you either have Asperger's syndrome or PDD-NOS but not both; of course, different doctors may have diagnosed you differently over the years. Psychiatric diagnosis is pretty fuzzy.