Am i fucken suffering from Manic Depression !?

I was on a trip to Italy - Milan - Florence - the works - and just got back to work. Beautiful place, Italy. I really loved the trip - possibly some of the most beautiful places ive ever ben to.

But the fucken matter of fact is that i suddenly have been feeling so goddamn low and all - i spoke to my dad today about it - he told me that 'at my age, i am blessed to be going through such a productive/informative phase and must take everything in stride'

http://en.wikipedia.org/wiki/Manic_depression

But i dunno, i think i have Manic Depression - Means - i have prolonged phases of Angst/depression/negative periods lasting 3/6 months in between periods of good life & productivity.

Are such periods of Intensive introspection / Thought / Loneliness / actually good for you ?

What i mean is , Is it like you're supposed to build on these thoughts and do the groundwork for your next period of productiveness OR Am I really a hopeless, fucken depressed asshole.