No, the test should not have had this affect on you, nor should the prep. Was you GI aware of how severly de-hydrated you were? This actually warranted going to the ER to get re-hydrated. Are you drinking things like Gatorade and orange juice? This will get you hydrated the quickest since they contain the potassium and electro-lytes you need, just water won't do this. But I feel you need to contact your doctor regarding your symptoms, as it may not be dehydration.
That's such a completely draining preparation, it's no wonder your still feeling under the weather. Why don't you try one of those sport drinks to bring your electrolytes to normal you must be deleted.