I hate laziness. This problem is one of those that just goes in one big circle. Similar to Goldmember the movie, when Fat health questions states "I eat because I'm unhappy, and I'm unhappy because I eat".
Anyway, what I mean by that is laziness prevents one from reaching certain goals. But despite the person's attempt to achieve them, the laziness, which is the problem they are trying to fix, becomes the problem that sets them back from doing so.
Out of curiosity, what was your life like since you were a kid? Did you generally have this sort of trend. or were you at one point considerably active, whether it was sports, or any other sort of hobbies.
If it is the case that you never have really gone out and experienced what the world has to provide, despite it requiring socializing and physical activity, the only thing you can do to change that is to go out and experience them whether or not you like it. If you haven't ever experienced it, and let the years go by, generally we all begin to fear change and have a natural bias for not wanting to try it later on. The only way you can discover if you will enjoy something then, is to just drive yourself to each task with an open mind and see if it is something you can see yourself doing. If not, keep moving on to the next thing.
I may be considerably younger then yourself, but I can understand the perspective of somebody who hasn't attempted to socialize and kept mostly to myself. I was like that for most of my teen years because of some issues, depression, low self esteem, etc.
College started and I decided to try new things. One of them for instance is dance. As you know, there is a stigma that most guys (straight ones) don't dance, I never would have thought myself doing it, after receiving so much racism about asians not having rhythm (all of which i took seriously back then), and it definitely didn't seem like anything I would enjoy, making a fool out of myself in the dance floor.
Turns out, I'm very good despite my lack of experience, it's been only a year when I first took salsa and swing lessons, for the last two semesters, I help teach that very class now as a "T.A." =P
Go out, no matter how uninteresting and unappealing it may seem to you, and just try. Have your family force you and support you on this.
Not to be a sore thumb, but we all eventually part this world, I'd like to personally think about that one fateful day, and make sure I don't have a list of things that I would suddenly just realize that I wished I could have tried to do.