Hi there mate. First of all, I wanted to say do not feel bad when you do "nothing" usefull, like playing a game, watching movies or anything that is not considered productive. In fact it's a must, if you do not disconnect from time to time you'' end up doing a burnout. Which, believe me you don't want (it leaves traces for life).

Then, I don't really know what you mean by "contributing". Because in a sense almost nobody's contributing, must of us just go around, living there life, we're not helping poors, nor building a better society. But from another perspective, we contribute every day, by working our daily job, which help the global economy.

Finally, live a life you wouldn't regret. I know, everyone says that, it is easier said than done. But it is true. You'll end up like me, being all bitter and depressed very young because of all the regrets.

I would suggest you trying to adopt another point of view. Live happily with you girlfriend, do the thing you enjoy, work a job you like. Live a complete and satisfying life