Schizophrenia is a long term condition, where psychosis can be used as a symptom or flare up (psychotic episodes, for example). In regard to schizophrenia, psychosis covers the "positive" symptoms of hallucinations and/or delusions.
In summary, assuming you DO have schizophrenia, you have both. Schizophrenia is the constant condition and psychosis is an episode of positive symptoms.