I'm going to guess mixed episode... I'm a little there myself. I guess it's the stress and fast-paced environment of my job, causing my mind to race and me having to have energy. Then the stress and the realisation that i just cannot get it right - that triggers the depression in me.
You need to look at circumstances in your environment and life, and see if any of them could be triggering you, and consequently be removed.
I really feel for you - it is terribly exhausting and painful