I understand exactly what you mean. I really think you should visit your doctor and say that you've been talking it over with your therapist, and that you'd like to know if you are suffering from dysthymia one way or the other. Explain that having a concrete diagnosis would really help in terms of your own recovery (because you'll know what you're struggling with).

Your therapist should be encouraging you to do that IMHO.

You could take a printout of the DSM criteria with you if you're nervous, and point out why you think it fits. It's the same thing the doctor or Pdoc will refer to.

http://www.behavenet.com/capsules/disorders/dysd.htm

Good luck! Let me know how you get on