That's how I started my 'opiate career.' I tore my ACL and was given 10 mg oxy's plus 7.5mg norcos. Even though I was taking like 2-3 oxys and 4-6 norcos for the first two weeks after surgery then tapering down gradually according to surgeons guidelines, I actually didn't get addicted and didn't feel sick when I stopped or when I tapered.
However, the 2nd time around I was in a car wreck (about 2 years after this ACL incident) and a doc rx'd me 45 norcos to last me 14 days. So even though it was a smaller script and I was taking less than post ACL surgery, I got addicted to them and found it hard to stop.
Before long I was eating old norcos and other pain meds that were around the house, buying oxy's off the street, then snorting h, and finally shooting h...
Personally, I wouldn't of even touched subs in the first place if I were you. Bupe isn't a weak opiate - it's much much stronger than norcos. It's prescribed in microgram doses for pain management and mg doses for hardcore addicts. If you're just using norcos please don't go down the route of taking subs.
Since you're already on them I would highly recommend you detox 10% per day over the course of 10 days, suck it up for a few days if you feel bad (loperamide, marijuana, valium, etc. will help a lot) and don't get mixed up with opiates again.