It might be helpful to have a conversation with your therapist about how you feel about his diagnosis. Because of the lack of precision in the diagnostic system there are going to be people who are hard to classify one way or another and they will be diagnosed differently by different people.

I would try to just focus on which symptoms are troubling to you and deal with fixing those. It sounds like Seroquel helps you also with anxiety. Is that right? At the end of the day, its about finding the right mix of meds (or no meds) for each person, rather than the specific diagnosis.

Even in Bipolar 1, with it's unmistakable manias. This can also be diagnosed as Schizoaffective Disorder, if the delusions persist outside of mood disordered periods. For people with psychotic manias, the psychosis can start to extend outside of the manic periods so I think people can go from Bipolar I to SchizoAffective over the course of time.

There's a lot of overlap between bipolar II and treatment resistant depression, as WC already mentioned, but I don't know that much about it. Some people think of bipolar on a 'spectrum' and some more as a cut and dry issue.