Hi, Steve, I am sorry you are suffering so. I do not believe you have bipolar, but rather depression/anxiety disorder, which is very common. Zyprexa is not a treatment for this, however. In order to be bipolar, you have to have had at least one manic/hypomanic episode lasting 4 days or more. Here are the symptoms:
Sleeping 12 hours a night is either a symptom of depression, or a result of Zyprexa, which is actually designed for treatment of mania and schitzophrenic psychosis. It is generally too strong for anyone else and can be the reason.
Tell you psychiatrist everything you have said here. If he doesn't change you to an appropriate medical regimen, (antidepressant and antianxiety, like Effexor and xanax, just one example), find a new doctor. Good luck!