I am addicted to the internet and haven't been outside in over four years. what hope do i have of overcoming this?

Seek help: Given the enduring nature of your troubles, the best chance of overcoming things would be to consult with a mental health professional. If you can make this difficult move, i.e. Setting up a consultation and getting to the appointment, you might have a leg up. If it's too difficult to get out of the house for the appointment, some practitioners might be willing to start out with a few phone calls.