Those disorders are all pretty hard to differentiate between, as they all include psychosis. Did they happen to say schizoaffective disorder rather than schizophrenia (or potentially schizophrenia spectrum)? Because that would fit perfectly well in the triad of mood disorders with psychotic symptoms. I can understand why a doctor might think schizophrenia, though, as psychosis can come up as a more prominent symptom than mood.
Differentiating these things is hard, because the doctor needs to know whether or not the psychosis is happening outside of a mood episode (i.e. mania or depression). Bipolar often presents with psychosis during mania and depression. Psychotic depression is when psychosis occurs only during depressive episodes and no mania is present. Schizoaffective disorder presents when psychosis is independent of mood episodes, but mood episodes are significant and recurrent. Schizophrenia has no diagnosable mood episodes.
This is why it’s so hard to get a diagnosis. They all interrelate and have overlapping symptoms. On the positive, many of the treatment options also overlap.
If you would like to get an answer, you could ask for diagnostic testing. However, this is still not definitive. I have a friend who had diagnostic testing done, but their doctor is thinking about getting the testing done a second time as their symptoms have changed.
I know having answers is nice, but try to focus on coping with your symptoms and treatment.
Best of luck.