Hi I Am 13 Years Old. And I Have Had

Hi I am 13 years old. And I have had bad breath since I was 11 I have suffered from it and have done everything to get it to disappear but it just doesn't work it's affecting my education and I'm doing really bad at school I brush my teeth daily two times a day and after I brush my breath still smells bad I chew gum but it just makes it worth what can I do?