Bipolar depressionWatch this thread
Bipolar disorder isn't the same as depression, although people with bipolar disorder do have depressive episodes, however, they also have manic/hypomanic episodes as well. They don't refer to it as bipolar depression/manic depression anymore either.
That's unusual, it's an old term. Anyway, yes, speak to your psychiatrist and ask why you've been diagnosed with it so they can clarify their diagnosis choice. It might help you understand yourself more too.
It's concerning your doctor didn't explain properly, if you don't feel like the diagnosis fits definitely bring it up with them next time you see them