While reading your post, I thought of two possibilities:
1) You may have developed allergies to these substances. You can't be allergic to anything you have never been exposed to, so the initial good experiences were not tainted by an allergic response. But once sensitized, another exposure might trigger an allergic response.
2) You did not say what form the oxy and hydro codones came in, but if they were paired with acetaminophen
(Tylenol) aka APAP
, and you didn't remove the APAP from the tablets you got, you may have been overworking your liver. There is a very narrow margin between an "effective dose" and a toxic (and potentially fatal) dose of APAP. The current maximum dose permitted by the FDA is 4 grams per day (and they are considering dropping that to 3.25 grams), while 8 grams can be a lethal dosage for some people.
If you took them in the form of percocet or vicodin (lortab), 5 mg of the narcotic was paired with either 325 or 500 mg of APAP. To simplify the arithmetic, lets assume 500. 30 mg would be paired with 3 grams APAP, and taken twice would mean being over the limit by 50%.
If you drink a bit of alcohol
regularly, or had several drinks that day, or take certain legitimate medicines (such as lipitor) the toxic APAP dose might drop to about 3 grams.
If this is the case, you may feel lucky that you got off with just feeling sick, and your liver recovered. From what I've read on the subject, if your liver was damaged by APAP and did not recover, you could have gone into a coma and died within three days.
Taking large quantities of drugs
like percocet or vicodin can be suicide, not because of the narcotic, but because of the APAP. For this reason, the FDA is considering removing such narcotic+APAP combo drugs from the market, so that the narcotic will be prescribable alone, as a C-II drug
, and if your doctor wants you to take APAP as well, he'll "recommend" OTC Tylenol for pennies a day.