I too think you are reaching too high. It seems you are looking for a concrete answer as to why you are bipolar rather than concentrating on how to manage and deal with it in your daily life.

I notice you refer to a therapist. In my opinion there are stark reasons differing between seeing a psychiatrist and seeing a therapist. I believe one should start with seeing the first; who can make that diagnosis and help manage the disorder with medication (which I believe is necessary). The therapist meanwhile can arm you with coping mechanisms and manners in which to manage the difficulties and resulting behaviors.

I understand the need to know; however, consider this, finding a reason in no way is going to change the treatment.