Take a feather, and run it along your skin, as lightly as you can, trying to catch that point where the irritation of almost but not quite tickling occurs. Capture that feeling. Remember it.
Now take that feeling, and stick it underneath your skin. And extend it, its no longer just that tickling, now there's pain too. Except you can't feel the pain right either. It's wrong. You absolutely know it is wrong. What else could it be, if there's painful feather tickles trapped under your skin through out your body?
When you have a feather on your skin, and it is causing a problem, what do you do? You make it not be there? If someone is seriously chasing you down with one and it is causing you this much distress? You would probably run and hide, getting away.
But now we're within your skin. And you want to run, you want to escape. That's the overwhelming feeling, wanting to run, get away. Your body feels wrong, you need to get away, you need to get away from the taunts, the pain, the flick flick flick of feathers, and tensing up of nerves misfiring. Feeling every bit of skin from the inside. Feeling the uncomfortable tingles and feeling every bit of air passing by.
You need to get away, run, run as fast as you can. How far can you get away. How fast can you go? What can you to to make this assault on you end, and how can you separate yourself from it? The faster the better. You must do it. You must.
But then, again, no, you can't. It's all inside. It's all in your body. You can't run. You want to; you need to, but you can't. There's no escaping by leaving.
So, instead, maybe you can make it leave? Maybe you can find yourself beneath this parasitic invader? Maybe you can make yourself feel better.
It's not parasitic in that there are actual parasites, but there's something taking over, and it needs to get away. It needs chased out. You need your body back, and you need it however you can. You are losing control, because your body has a mind of its own. Your body is trying to get rid of its attacker, even though its attacker is itself. The attacker must be gotten rid of. The attacker must be chased out.
You'll get rid of it, you'll get rid of the invader, even if it means harm to yourself in the process.