Hmm, I'm not a doctor but I've watched a lot of discovery channel. [img]http://www.**********.com/iB_html/non-cgi/emoticons/wink.gif[/img]
I agree with Schloaty, it sounds like he is suffering from a sleeping disorder, possibly from a breathing problem. If he isn't entering into a deep enough sleep state, he would be tired and weak. The lack of sleep could also weaken his immune system and explain his fevers and throwing up.
You could try video taping him sleeping and seeing if he gets full paralysis so he isn't moving when he sleeps.
Also, a long shot but you could check the environment for the deadly mold and or some kind of pollution that isn't agreeing with him.
You might have to have him knocked out somehow so they can get a blood sample.