Your work is awe inspiring. I wish I was able to draw, but all I'm good at is writing. Man, what ever has you down, I'm sure it's not permanent. Just take a break from things and relax. The artistic itch will come back to you, even if it comes out as nothing more than an ink blot. Go hang out with friends, and just put the art stuff down. Doing what makes you happy, may not make you happy, but personal interaction is scientifically proven to be uplifting, even if you retain feeling like shit. I've lived with depression for 18 years now. I'm only 28. How have I managed to not only stay alive, but keep on going to now? My over-active imagination. I'm sure you'll get yourself upright again. Feel free to hit me up if you want to vent. I even have a teamspeak3 server, if you prefer talking. You don't know me, and I don't know you, but people are more important than the bounds of who we know. If you don't reach out to me, reach out to someone. Tell someone you're not feeling quite right, and see if they'll help. Even if that help is just holding onto you, to keep you feeling safe. Anything is better than feeling alone, unproductive, and depressed. If you let it well up inside, it will only get worse.

One thing someone wiser than I said, but it helped me.
Imagine someone makes a drawing with a flaw or two. Is "you suck at art and should quit." or "you're a failure at everything." reasonable critique?
We can be rediculously cruel to ourselves in our own heads, and shouldn't put up with it if you wouldn't put up with it from another person.