Dysthymia is supposed to be a less severe form of depression that occurs chronically for at least a couple years. Major depression is what encompasses those more debilitating features that you described. And you're right, an episode isn't a chronic thing. But Major Depression can have a "chronic" specifier. That's why it sounds like you experience something more like major depression: chronic than anything else. And it's entirely possible your therapist has that specifier somewhere in his/her diagnosis. Really, Dysthymia is supposed to be milder depression over a long period.

As for the DSM-5 change, this makes sense because often times it can be real hard to define the fine line between when someone is experiencing a particularly debilitating depression over time, or a somewhat debilitating depression over time. Where exactly is that line? And since that's so vague, do away with the line entirely and just call it all persistent depressive disorder. That's the mindset anyways.

So, neutrino, you're absolutely right. It's unfair to categorize what you experience as being merely an episode. But it's equally unfair to classify it as a mild depression in the case of dysthymia. It may be helpful instead to see it more as chronic major depressive disorder or as persistent depressive disorder as Rohag pointed out. I hope this helps some. Either way, we're here for you!