After trying multiple antidepressants and feeling worse(along with other attempted treatments), my Doctor recently mentioned that they think my depression may not be unipolar after all.  

I'm not convinced because I don't see any real manic periods in my behavior/feelings. Is it possible that my periods of simply feeling like existing is a little easier are the manic periods?  Or for instance, I recently actually felt more motivated to get things done... could that be the mania?  To me, the level of motivation I experienced just seemed like something that someone without depression would experience normally, it didn't seem like a crazy level of motivation that would be alarming.  Thoughts?  Experiences from anyone in a similar situation?