Depression is depression. Bipolar is hypo/mania, depression and possibly mixed episodes.

What can happen, though, is that someone receives a diagnosis for depression, and then later they get a diagnosis for bipolar disorder, once it becomes clear to professionals that they have it. This often happens when someone has a bad reaction to an anti-depressant and becomes mixed or manic from it, but not always.

However the bipolar disorder would replace depression as their diagnosis.

Most of my episodes are mixed states, either irritable depression or dysphoric mania. You might consider researching mixed states/episodes to see if you identity with it, at all. My BP was hard to recognize as-such at first because of how mixed I was most of the time.