These two Axes are orthogonal. It is not a complete change of the dx but an addition of a new Axis.

You said the original dx of schizophrenia was given very quickly. Was it in context of an inpatient stay? Were you hallucinating, having delusions, having a psychotic break? If the symptoms are severe, acute and obvious enough, the schizophrenia diagnosis can be given quickly and yet be correct. It is more for bipolar affective disorder that one needs time observing the patient in different phases of the disorder to arrive at a fitting dx. But bipolar is an episodic illness by its nature.

Are you on an antipsychotic medication? What are you currently taking? What is your rx?

I agree you need to see your psychiatrist again soon.