Everyone is different. Being larger or smaller has a big impact on how the meds affact you. So does metabolism but in a different way.
Some people will pass out and be loopy after just 1 pill. Others won't. I have an incredible tolerance to any substance and 5-10mg wouldn't have cut it for me when I was starting, either. In fact, I take 40mg of percocet at a time now. That's 8 of the 5mg pills at once. That's a lot by medical standards but just my reality. One man's 5mg that works is another man's 40mg that works. Whatever it takes I guess.
In your case, I would suggest upping your dosage by 1 pill until it works. I am not a doctor so take what I say with that in mind, ok? Try 3 pills next time and see how that works for you.
Keep in mind the tylenol intake as well. You're allowed 4g a day, or 4,000mg. That is just 8 pills if you're taking the 5/500. Anything over that can cause liver damage. Many addicts, like me, take well over 10,000mg a day and it is really messing up our livers. That much could prove fatal for you though, since you're new to this, so keep that in mind as well.
Also, keep track of how much meds you have and when you get them refilled. If you're taking more than you're supposed to, you will run out early and be left without anything to take until you get another refil. Withdrawals are hell. Doctors won't give early refils 99% of the time, either.
Good luck and feel free to ask any other questions.