Do not act hastily and D/A. Don't play the Org's game. Simply miss meetings on a regular basis. Stop field service immediately.
When
Elders call you to arrange a shepherding call to find out why your
failing to live up to their expectations, simply say, "Thank you for
offer, but not at the moment. There are things I can only talk to
Jehovah about, but if things change, I'll call you."
Although I strongly agree that you should not DA and should fade instead, do not be afraid to tell them that you are badly depressed and are trying your best to rely on Jehovah.
They will then avoid you.
MANY, MANY JW's are severely depressed.
I went through a prolonged depression (over 10 years - thought of suicide every single day - 24/7).
Oddly enough, the more meetings I missed and less field service I did, the less depressed I became.
I have not set foot in a JW building in nearly a year - and my depression is GONE.
You may not realize it yet, but at 21, you are darn lucky.
Many of us here went through decades of torment before we woke up all the way.