Explain your concerns to your doctor when you see him/her. I know the fear you are going through first hand. No matter what the DX is, you will walk away with more knowledge than you have now.

Keep in mind that some people have more mild PPD or schizophrenia and some have severe bipolar. Unfortunately, there is no better mental illness. It's how you function and are able to cope with it which determines its severity. I wouldn't worry about the DIagnosis as much as the symptoms and how you learn to manage them. Best of luck. I hope you will keep us posted.