For me, what you described has always been a natural cycle... Huge bursts of creativity followed by a "rest" period (I've been told that that's when creativity rebuilds).  If I try to push myself to create during the down time, I get frustrated and don't make anything worthwhile.  Maybe you're going through a rest and rebuild phase?

Either way, when you're an artist you're born to create - it's not something you'll ever permanently lose.   ...And you're certainly not alone in feeling like this!

Hang in there!

I know what it means to be depressed and an artist at the same time.  Don't think in the suffocating box of galleries for encouragement...unless the sterile and uptight surroundings drive you to create.  Uplifting people and events are the usual ticket for encouragement.  Encouragement fosters participation...participation encourages creativity...and creativity without burdens of the box you were in, gives you permission to diversify from your little habitat and discover new things.  A relationship with the main Creator wouldn't hurt either.  This relationship with God won't vaccinate you from infectious let-downs from negative influences, but it gets you past these fugue states of not producing anything fit to keep.  Stay around people that care about you...even if it means only one or two friends...they don't even have to be artistic, either.  Also..go where there is natural scenery...that always gives you literal breaths of fresh air.  Remember that strangers even care about you...like the artists on this site.  God bless...and yes, blah blah blah...that doens't hurt anyone...and you can blah blah some steam off the top of the stew!