Hey, this is an interesting thread.
Think of it in a VERY simple way:
Schizophrenia - is basically, "psychotic symptoms..."
Clinical Depression - is basically, "Depression to the point where it effects all areas of your life..."
The thing with bipolar - which CAN be depression with hypomania (Bipolar II) can give you psychosis when you are only depressed... It doesn't matter what mood you have when or whether you have psychosis before or after your mood changes. Most of the time - psychosis changes your mood - because it makes you feel uncomfortable... Obviously - if you're hearing voices - that are talking about you - voices that redicule you - you're going to be mad, sad, depressed, etc...
One thing you gotta realize - ALL these illnesses are SO closely linked - they're all basically invented illnesses with specifically chosen categories of symptoms... Thats ALL they are! You can have bipolar, then you could have schizophrenia... But then you could have BOTH... Different doctors will come up with different diagnosis's when you go in for second or third opinions... Its just how it works. Its all trial and error - there are NO answers...
My opinion - is that you have clinical depression. And that if your depression gets low enough - you become psychotic. See - thats to be expected though. If anyone gets stressed out - to the point where they become depressed and are unable to look after themselves... They can and do become psychotic. Its the brains way of saying, "Overload... Don't know what to do with all the stress..." So you're mind takes it out on you. First - physically, then emotionally... And once it gets you down low enough - you become overwhelmed and THEN - you can become psychotic. (Its basically the bodies last resort of dealing with stress)
Anyways, don't think so much about the DIAGNOSIS; as to the importance of looking after and dealing with your SYMPTOMS... Learn to ACCEPT your symptoms - and learn to deal with them one day at a time. You'll pull through.