Dude listen to yourself, who're "they" that you're so worried about? Confidence is self-belief in your abilities and accomplishments, it's why 10 people in class can laugh at you for stuttering and you flip them off and say they probably smell like dog water, be your own fan. It starts with liking yourself, if you don't like yourself then start from there, write down 10 things in a notebook you like about yourself and repeat it over and over, hell, write down things you can do better than other people and repeat it everytime you engage with people.