@Erik: Yeah 14-16 hours/day is addiction. I consider myself a big internet consumer and I usually peak at 5 hours/day, and then only 'cause I'm half unemployed at the moment. Anyway I get uneasy and all headaches when I sit more than two hours at once at the keyboard, so that makes matters easier...
But I can perfectly relate to what you said about being on the way to your exam, then suddenly not feeling like taking it and basically buggering off - and also gathering everything necessary for studying and once you have it leave it in a corner for spiders. It's one manifestation of procrastination, which is not to be mistaken for laziness (even if both make good partners and are difficult to differentiate). It is a kind of pathologic compulsion which can take you to the extremes, sociopathy and the like.
Well I guess we're all there a little already, but I agree with JayKeeley: you should force some outdoors stuff upon yourself. Not necessarily get friends for the sake of it. Most people are vain even if it's seldom their fault. I dunno... I spend hours just walking around with my camera, I practice a few sports... and I can tell you, it's not always like I enjoyed doing this in the beginning, but you get used to the impression of doing something healthy for yourself. The damn "first step" barrier is all it takes.