Why's my baby quiet most of the time?

Im a first time mom at mid 20's and my baby is one year old now and 2 mos, and im wondering why he's quiet most of the time. Is this normal? well, he cries when he needs milk and changing diapers, and after that he sleeps again. It's very difficult to make him smile and when he smiles, you have to wait for a long time to see him smiling again. He doesn't display a lot of reactions like other babies do (a lot of babytalk, cries a lot, laugh and smiles often, move a lot, responds to music a lot etc.) One time he shook his head to the music and i was happy seeing him enjoying. But he's seldom doing that now. Im worrying if there is something wrong with the emotions of my baby because i was having a hard time all throughout my pregnancy. I went though a lot of depressions. I don't know much about babies. Can you educate me on this? He's always quiet most of the time and i think he is shy.