I have this weird burning sensation in my stomach and it's been 12 hours and it hasn't stopped, including taking antacids. what do i do?

Stop the antacids: If I were you I'd stop taking any more over the counter medication (and nothing from the parent's medicine cabinet either), make sure you are well hydrated, eat if you feel hungry, but not too much....if nauseous limit to softer types of foods such as pudding, crackers, apple sauce, etc. and tell someone in your household to set up an appointment for you to see a doctor if things don't settle soon