Okay, am I just a burden?

I'm 18 now, and I ran away from my previous guardians to come live with my grandparents.. I see my mom sometimes, but I'm better off without her. Believe me, I have tried to get a job for a whole year.. never had ANY luck. I would try now, but I plan on moving as soon as I graduate high school, a month or so.. it'd be silly. I'm driven to school by my nan.. who has a job she constantly works at, I bunk in my little brother's room.. I do whatever I can to help around the house.. but, my grandfather has insisted pretty much the whole year.. that I don't care about anyone here, and I don't help with anything at all. Either way, I don't feel like I fit in here at all. But, kind of sucks when you don't even feel like you have a family, but screw it.