Of course, only a qualified psychologist can diagnose bipolar disorder. The difference between bipolar I and bipolar II, in my understanding from taking a PhD level course in clinical psychology and having an ex-husband who has been diagnosed, is that type II does not typically have the "manic" phase that most people think of with bipolar disorder (previously called manic depression). Instead, the depressed phases alternate with an angry, irritable, distracted mood.
There are different levels of severity of any mental health issue, of course, but my experience with bipolar is that a person is barely functional without proper medication. They are unable to hold a job, or be productive in their lives, and people surrounding them will be suffering significantly also. When my ex was applying for disability, I did some research and found that a diagnosis of Bipolar Disorder significantly increased a person's chances of receiving Social Security disability because of the experience that people with this disorder are often unemployable. This is a serious diagnosis that could have multiple effects on a person's life.
There is another diagnosis that falls between depression and bipolar, called cyclical depression. This type of depression affects a person repeatedly, with periods of near normal, followed by another phase of depression.
I would talk with your medical professionals if your medication does not seem to be working.