Diagnosed with Major Depressive Disorder, but is it really MDD?

So I have just had my second Psych appointment after 7 years of no treatment. I've been given the diagnosis of Major Depressive Disorder. I have a week until my next appointment so I'm asking here in case anyone has an answer. I have the symptoms of MDD however, most of them do not show unless I get into a legitimately bad mood. I have the thoughts of sadness on occasion and the lack of interest but I only become seriously depressed usually in response to stress or just a bad day. However, when I do encounter such a situation my depression becomes similar to Psychotic Depression at a certain point. Does anyone know if this is MDD, PD or both? I'm working on the impression that MDD is consistent with the symptoms but mine is situational to a certain degree so I'm confused. Thanks!