Well, I sure as hell ain't a part of your imagination, perhaps you are a part of mine?
Jokes aside, hang in there. Its a horrible unreal feeling, i know, but the world is indeed real, and so are you. For me, religion helps me stand fast in this fact, cause god did not create the world just in our imagination.
My advice to you is to get out there. Speak with people, you family, friends. Work out, do something high intensity. Do everything you can to express yourself. Most importantly, do everything that you have become afraid to do before the fear gets worse.