Am I extremely lazy or am I depressed?

For the last nine months, literally all I have been doing is laying in my bed. Out of 24 hours a day has, I spend 22 or maybe even 23 (or even more) in my bed, on the Internet, every day. I only go out when I have to go to the store, which is about a minute and a half away from my home, but even that represents a burden to me and it takes me hours to get myself up and do the task. Other than that, I don't leave my room. I try to avoid meeting with friends as much as I can. I make up excuses why I can't go meet them. Only for few rare times in these last nine months did I genuinely want to go meet a friend. My mood is as low as my self esteem, and my self esteem is non-existant, except for periodical moments during which I may have high opinion of myself, but such moments last for few hours at most, if even that long, and it's more of a feeling than an opinion.

I feel terrible about this, I know that I am a useless member of my family. I try motivating myself to start studying (programming, which I can do online), I fail. I try forcing myself, I fail. So nothing works, neither positive attitude, nor just trying to do thing using will power, no matter how much I don't feel like doing anything, but no progress. But when I think about it, I only want to change not to disappoint my mom and to help her, but if it was just for me... I don't care about myself, nor my life, at all.

But why can't I change? Why can't I persist doing the right thing? Am I just lazy or is there really something wrong with me?