I went through all that unmotivated depression crap for several years before I finally snapped out of it. It is a really strange feeling - it's like you are more motivated to dig yourself deeper into a pit of unworthiness rather than to climb out of it. The deeper you go, the longer the climb to get out... then you justify the power it has over you and you say you will be that much stronger when you finally climb out because of how much more effort it required to go that much further. You test yourself and force yourself to believe it is for the best. You keep pushing lower and lower until you finally can't see the light at the top of the pit... You won't scream for help to the ones you love most because you feel like you would be a burden in their lives... you instinctively feel the need to protect them and you ultimately feel trapped and alone.
That is how it went for me anyway. I went a LONG way before hitting bottom! The scary thing is... I think I was right; the further down I went, the stronger it made me in the long run. That, or I was overcome by a creature of the dark that will never leave me... BUHAHAHAHAHA... shrug.
Not that you want advice, but the best advice I could give is to lean on your wife when you need her the most. The difficult times are actually less of a burden on her AND you when you face them together openly. Of course, I have been single my whole life sooo...
Sent from my "two hands on a keyboard"