....Now, with plugging.
I initially thought codeine had to do a first pass metabolise through the liver, then on into the bloodstream. With plugging it hits your bloodstream first, before the liver. It will eventually get to your liver but from what I've read/heard it can effect it's potential high(please correct me if I'm way off here).
Codeine is a prodrug - it must be pass through the first pass metabolism to have any significant effect (basic physiology). From the intestines the absorbed compound + blood (+ other goodies) just travel from the small intestine (particularly from the duodenum or to a lesser extent jejunum), via the port vein to the liver (to be fully metabolized - following the basic acronym
A.D.M.E). While IR will eventually make it to the liver, PO is the best route in this instances (minus the issues of the acidic environment of the stomach [by the time it passes the pyloric sphincter into the small intestines the environmental pH is ~6.5).
......now everytime ive done a cwe ive felt next to nothing.......
All the drugs you've mentioned are metabolised by different enzymes. So it doesn't surprise me that you've found a drug which you
cannot metabolise. 10%-12% of the Caucasian population (different percentages for different races, won't go into here). Essentially you're a
hypometaboliser of codine. Which means that the enzyme you're body creates (due to multiple reasons. I can go into details but if this explanation will suffice than great!

) is either deficient or non-existent (less common). This means that your body is unable to metabolise codeine to morphine which is where you get all those wonderful effects (codeine, as I said being a "prodrug", means that it itself have no biological activity). So essentially, you take codeine, you're body cannot metabolise it, it hangs around in our system for while until it is expelled (while this "hanging around" occurs damage to cells/tissues/organs may or maybe not coming damaged, this is still up for debate).
First piece of advice; don't both taking codeine to try to get high! It wont work and more than likely is causing damage.
Second; go to your doctor, say you've noticed codeine doesn't have any effect on you and ask for a genetics test. The reasons for this is the two biotransformational pathways codeine is used to convert to morphine (an enzyme called
CYP2D6 and a reaction called
Glucuronidation) are both HIGHLY expressed yet with wildly varying phenotypes cause issues like this. The only reason I say (although I don't wish to alarm you!) to see your local GP is that many, many drugs are metabolised by the CYP2D6 isoenzyme which
could lead to possible problems later in life.
Have a look at the links (I know they're only wiki, but a good starting point). Might be something you're interested in.