I'm not sure but all I can say is that really fuckin blows. Sorry to hear it. Hope someone can give you an answer.
Well, back when I used to CWE codeine pills I could drink the foul shit. Now I *can't*. Absolutely can't stand the taste, cannot stomach drinking it. Also, back in the day, snorting 2CB was a fairly mild affair. Now, crippling nausea and a streaming nose and eyes are the order of the day. When your body is suck of a substance, I guess it says, "hey, quit putting this is in here!" However that wouldn't explain the hydromorphone thing cause you hadnt had that much experience...
heh i wish oxys did that too me, easier to quit them. but i dont think i know why this is happening unless you stopped abruptly and your brain isnt used to not using benzos. 3-4 xans is quite a high amount/tolerance. id be surprised if you didnt have withdrawal. as for oxys i dont know, some people react differently to opiates, but i dont see it just changing like that.