Try to write in a journal. Summarise every day, and try track a pattern. It will help you understand yourself better. I too was first dx'd as depressed. But after a while, you notice there are periods where you are happy, or even VERY happy (mania) - at this stage a pdoc will start looking into a dx of bipolar.

I'm sorry you are battling to come to terms with the dx - are you seeing a T to help you understand things better?

Dealing with Bipolar takes both meds and lifestyle changes (In my opinion) - keep asking any questions you may have!