How to help self confidence, please help me?

Well i have almost no self confidence. And its getting pretty bad. Like when people come over i go up to my room and hope they dont see me, and its not that im shy, i was thinking and its that i dont want them to think "that kid is ****** ugly" or "omg, im glad im not his mom" not those exact words obviously but like that, because i look pretty bad im really tall (6 foot 8) and i weigh 320 lbs and i have hair that completely engulfs my head and i wear a torn up biker vest and camo pants ussually, and i hate how i look but im afraid to look any other way because im afraid ill look worse, and i hate going places because everybody looks at me, and next year ill be a year senior in high school and there will be a whole bunch of freshman who think im a criminal, and i pisses me off because im as nice as i possibly can be to everyone i meet, and alot of people think im a mean kid, and i cant take it, please help me, like how to dress socially scceptable and help me like myself and who i am