For schizoaffective, you have to have the psychosis part (the part A criterion for schizophrenia) for at least 2 weeks without being in the middle of a mood episode. If you only ever have psychosis while in a mood episode, then it's probably bipolar with psychotic features. But it doesn't really matter from a treatment standpoint; you'll need an antipsychotic and maybe lithium/an anticonvulsant mood stabilizer as well to control the bipolar and the psychosis either way.
Because of the need for 2 weeks of psychosis in the absence of a mood episode for the schizoaffective diagnosis, it can take quite a while to get a definitive answer, since some people are in mood episodes almost constantly.
I had same problem as you and question , they still don't know if it's Schizoaffective or Bi polar with psychotic features
One medication that will not work if you have schizophrenia is lithium. If you are taking lithium and it is working nine times out of ten you have bipolar not schizophrenia. Look up lithium and schizophrenia online and you will see it does not normally work for schizophrenia patients. I was on lithium I did not feel any better on it and eventually it hit my kidneys and I had to go into the hospital for seventeen days to get the lithium out of my system and have dialysis.
ILADVOCATE is right, about the mood episodes correlating with psychotic features for BP, and so this is where the mood chart can help. I would not worry too much about getting the right 'label' as the treatment is basically the same for both conditions; an antipsychotic and mood stabiliser. I have suspected that I had schizoaffective in the past, but either way, it would not make a difference to my medications as far as I'm aware.
I have schizoaffective disorder (with the bipolar aspect) and before my current recovery I had psychotic thoughts and delusions at all times (depending on my response to treatment as well of course). I do know that for schizoaffective disorder delusions and psychosis occur at all times whereas in bipolar with psychotic features they occur only during moodswings. You can speak to your psychiatrist about this but also keep a mood tracker and print out the results for your psychiatrist as that can be markedly helpful as well.