Am I so bad and embaressing?

Why people always say that I am quiet? I always take an effort to talk, but they always say that I am quiet and it getting on my nerves, and I think what they think of me. I just turned 18. Yesterday I was in my cousin's party and it was in a limousine. I live in a different city from them. There were girls and boys, and I had no idea what to say, sometimes I just asked questions and thats it and answered if someone asked. There were many people and they were telling me that I am a quiet guy. Can someone tell me what to do? thanks.