Im feeling a little down, how can i cheer myself up?

Im 15 and well.. im a dropout, i stay at home and play computer games mostly, and well my friends still go to school, and when they finish school they usually come online and play with me too, but lately i've been feeling like none of them want to talk to me or they're too busy or have better things to do. Im too lets say "ashamed" to go back to school because of all the work i've missed out on, and i know how this is meant to be one of the most important years for me due to all the test i have at the end, its just im a very shy guy and dont speak out much, i just need some cheering up, help or advice would be greatly appreciated.