I always got a headache, and sometimes I took the pill, usually contained acetaminophen, will this damage my health?

Not really. Tylenol (acetaminophen) is a very safe medication in healthy people. Make sure the daily dose does not exceed 4 grams.
Probably not. As long as your liver is healthy and has normal function (you can check this via lab testing), your health is probably fine. Remember to keep your total daily dose of Acetaminophen to a maximum of 4000mg per day.