Dont quit your job,

While it is possible the testing place is taking a long time that is quite a while. There is a decent chance you were found positive by the antibody test and now are in que for GC-MS confirmation which takes more time.

Why not just call the employer?
Sorry to get you worried but I would be but I have had long waits and was fine. Was it just a drug test? For example I have had full physicals and that can take quite a bit of time to get all the results back from and could have nothing to do with the drug test.

Also if you have not smoked dont, you maybe able to demand a re-test claiming it was a false positive. If you have not smoked you may be clean by now.