[Thirteen]

I think as you said, Shawn is your way of coping with things. I think the biggest thing is the depersonalization and the derealization in MPD (DID). I'm not 100% sure on this, though.

But with the fact you realize that Shawn isn't real, I think you're just dealing with alot right now, and having someone there who you've had in your mind for a long time now is your mind's best way of dealing.

Even though it's highly unlikely that you have a Split Personality, you should probably still talk to your therapist about this. Not only should you probably find a more healthy coping mechanism (if this is all it is), but also, seems to be affecting some aspects of your life, which isn't good.