You may certainly feel that way...because of how you feel inside. That's what I like to call the "delusional" side to depression. We are so focused on how crappy we feel that we assume others think of us as worthless too.
Depends on who your hanging around too. Co-workers and such can be very "wolf pack". Gotta watch out for that.
They'll pick up on your "negative vibes"...if you will...and just think your anti social and not talk to you.
I suggest getting to know yourself more. Learn who to open up to and who to avoid. If things are bothering you...smile more...even if it is fake, people don't know....then excuse yourself and walk away for some "down time".
I'm sorry your feeling so bad...but I've been depressed almost all of my adult life. I can assure you that you can live with this and survive. See your therapist, take your medicine and please try to understand yourself more and that "special gift" that is definately inside you waiting to "blossom". You'll find it if you try hard...and it will be beautiful.
m.b.