Actually, I have no options either at the moment. I didn't feel it necessary to tell them that when I asked my question though. If you feel better no making it sound so ultimatum-like though, you could simply tell them that you desire a diagnosis. When they tell you that they are more interested in working on symptoms than nailing down a diagnosis, then ask them this:

I understand. Ultimately, who gets to make the decision determining how I spend my time here?

No ultimatums. No threats. Just a question. At that point though, I think a diagnosis will soon appear.