i do not think your past alcohol abuse would have any effect on the strength of your pain medication...not a doctor so not entirely sure on that one..
As for the 5mg percocet being strong....its just comes down to your opiod tolerance. I was able to swallow 80mg oxycontins like they were breathmints because of my usage of heroin. Be careful about taking to many of the 5mg percs at a time because they contain a whole bunch of acetaminophen (aspirin) in them.
Best bet is to go to your doctor and see if he can switch the medication and give you a different active opiod (like hydrocodone or oxymorphone etc etc) Hope oyu feel better man ~~ scott