Body Snatched And Blind

What's this thing I've found in here?
Its true intention I do fear
For why choose me from all the rest?
It's a bloody fool with sickening tests

So what's this thing inside of me?
Please help me out, for I can't see
The beast has gone and ate my soul
It's five full senses that it stole

Just help me out and clue me in
Before I'm tossed in the loony bin
I don't know why it picks on me
It'll kill me soon, just wait and see

I've figured out what the defect is
And why it's forced this horrid quiz
I'd ignored the problem growing strong
The monster's me, is that so wrong?