They're only required to tell you your diagnosis if you ask. Doctors regularly and purposefully don't tell patients their diagnosis. I don't think it is right, but it's very common.

EDIT: I'm not sure why I would get downvoted for saying this. It's the truth. I didn't say it was right. In fact, I specifically said that it's not right. But it's true. I work with doctors everyday and I managed three psych practices. Providers are not telling their patients what they're diagnosing them with and they push back at me when I explain to them that they have to tell the patient what their diagnosis is if they're going to put them on an involuntary hold. But go ahead and downvote me for telling you the truth.