Yes, job interviews are always hard, especially with our backgrounds. What you have to keep reminding yourself is that your medical issues are yours alone. They have nothing to do with the job. You don't even need to be thinking about them in regards to this interview.

Ask yourself this:
Will you do the job to the best of your ability?
Will you be there, clean and well behaved, each day?
Will you spend your day focusing on the job and not goofing off?
If you can say yes to most of the above then you aren't faking anything, Hamster. You are trying to remain a functioning member of society, something to be proud of. So if anything, you should go into this interview feeling proud of yourself instead of scared of "being seen thru."

You can do this. Keep a smile on your face, happy thoughts in the back of your mind, and walk in there ready to knock 'em dead with positiveness. They'll never know what hit them!