Best exercise for extremely obese?

I am 15 years old. I weigh 430lbs. I don't feel comfortable going to the gym because i get constant stares, giggles, and pointing from across the room. There was even one time a group of @$$wipe jocks came over to me, taunted me, teased me and made fun of my weight and wouldn't stop until i left. any suggestions for a work out or diets?? im extremely addicted to sweets! help please!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!…