Loneliness

Why is it that when I am often at home I'm very outgoing with my family, but in public I can come across as quite shy? I mean, I am a very friendly person, its just that I often don't know what to say to people, and I don't want to make a fool out of myself. I think when I get older I will be the type of person who will only have a few close friends, rather than many friends in general. Of course like mom often says it could just be the environment that i'm in. For example, in the other neighborhood that we lived in I had a nice group of friends and was very outgoing.But ever since then, I've been so quiet. But I did surprised myself by speaking a lot in the recent college english class that I was in. A lot of the times I prefer to be alone because it helps me think clearer, but at the time I don't want to become a recluse. When I was at school even though there were a lot of people, I still felt lonely and couldn't relate to many people. But I still need some kind socialization.