Is it possible to gradually adjust my antibiotics (amoxicillin) schedule(say,taking it every 11 instead of every 12 hrs),so times are more convenient?

Yes: The time issue is more important when an illness is serious and the med is given intravenously. When taken as an oral med for a common illness you have room to fit the dosing into your lifestyle. Adding the event to something you do every day also helps you remember all doses. Taking it when you get up & then 10-14 hrs later will be okay for most cases.