Sometimes with depression all you feel is numbness. In fact feeling like a "walking shell" is a very popular feeling. Are you taking meds and how long have you had depression?
Depression kind of makes you feel as if you are in a holding pattern. You are either waiting to feel good or really bad, I think that is why we feel numb.
If this is something that persists and you dont have a counselor, I would definately look into finding one. In most cases of people that feel as you do have underlying issues that are occupying you subconciously. Only talking about them helps.
I hope this helps in some way.