I've just been reading advice columns, so if this sounds like an advice column, I apologize.
I'm sort of perplexed as to why you think volunteering precludes a social life. You usually meet people while volunteering, and I've certainly done volunteer work that was very productive, fulfilling, and helpful, and that ended with us all going out for a drink after. But that isn't really the center of your post here.
Not everyone is a highly motivated type A personality who knows exactly what tomorrow will be. Just relax, consider what you might want to do, and enjoy your time being young. If you get through university and still have no idea what to do with your life, you might have a problem, but even then not a huge problem. I finished my bachelor's degree 4 years ago and only recently really decided what I want to do as a career. If you have trouble feeling passionate about anything, that can be a sign of depression or some shit. But if you still get excited about that book you're reading, or hanging out with your friends, or that girl in the third row, or that amazing pie they serve in the student union every Tuesday, you're probably doing just fine.