I believe you can find statistics like that on Dr. Phelps website: Bipolar II, Mood Swings without Mania; Brain Tours; Stress and Depression; Hormones and Mood; and more...

At the very least it sounds like you have treatment resistant depression, which means you could benefit from medications typically prescribed to individuals that have bipolar disorder. If your doctor has recommend lamotrigine to you, take him up on his offer. There is no definitive test, but the response you had to Prozac is a hallmark sign of a bipolar spectrum illness. How they label your illness is secondary to feeling better, I think you would feel better with the medications your doctor is recommending.