Not taking care of yourself, as well as not getting enough sleep are 2 signs of depression, however, your self awareness is remarkable for your age. Knowing what is holding you back is the foundation to pushing forward. Excessive video game play, as well as time on the internet, will usually lead to antisocial behavior, as well as low self image and the feeling of isolation.
As someone stated, get out and ride a bike, play some football, or even pick up a small part time job. Keep yourself occupied with activities that include others, even if the people surrounding you aren't "friends". It'll help build the social qualities that you'll need as an adult, and it'll expose you to other developmental experiences that you'll need.
The key is to start small. Think of your problem as a mountain, then break the mountain into individual boulders. Each boulder should be a small goal, such as reducing Halo time, then limiting internet time, then working out, or hanging with friends, doing homework, ect. Little by little, work your way out of it, as it'll be easier to rationalize and will develop your self dicipline.
Hang in there. You seem like a bright kid, and I'm sure you'll be up to speed living the enjoyable life you deserve.