Gigabyte
I think your last post stated it best. "I am uncomfortable telling someone that I'm having trouble with depression" and maybe add "but I am telling you because I need help".
You can possibly add what sophiesmom said "Simply (sending this) email(ing) has taken a tremendous amount of effort and you don't know how to start," adding "but I'm not comfortable coming in for a face to face right now."
That may be sufficient for your first email. Your counselor should respond appropriately and the process will start.
I found when my depression really hit my mind was all over the place and if I tried to explain what I was feeling it would have been a rambling mess. Your counselor will know what questions to ask.
Good Luck, Gigabyte.