I've been diagnosed as having a psychotic disorder not otherwise specified, with a secondary diagnosis of schizotypal personality disorder. Anyone know what secondary diagnosis mean ? Does that mean I've been diagnosed as having two mental illnesses ?

No. It's just medical terminology. It's the same thing.

It means that you present a few symptoms that correspond to the schizoypal personality disorder in the DSM-IV, while most of your symptoms sustain the primary diagnostic of psychotic disorder.

The diagnostic criteria for schizotypal personality disorder are not sufficiently sustained.

It doesn't really mean you have two mental illnesses, but it means you do present symptoms of two distinctive disorders.

I hope this helps.