There is nothing wrong with asking your doctor directly.
I often ask my doctors: What is my diagnosis? How are you coding my "case" for billing?
They tell me.

One doctor thought I was in a really bad place when he had changed my diagnosis. He did not say anything. A little while later, I'd thought to myself: I think I have BPII.
I then asked him and he hedged on this. I then told him to please not treat me with "kid gloves." He immediately came clean and told me my new diagnosis and why he had changed it.

Sometimes, doctors hold off on telling their clients because the client is not doing well. This is considered "ethical," if in the doctor's judgment, informing the patient might put the patient at a further risk. For instance if a severely depressed patient is suicidal and the doctor feels the patient will be increasingly hopeless/suicidal if given the diagnostic info at this time, it is ethical for the doctor to withhold that information until the patient is in a better place.

There can be a discrepancy between the diagnostic info we have been given by our pdocs and the info with which our insurance is billed. I do think this is the cause for the differences most often. There can also be other reasons. Just ask!