In the beginning several days after I got my baby I just fill his water dish with clean water and place him it. He seems to enjoy in the beginning, and then I put food out for him.

What I think is maybe yours was kept outside. Sometime that could be a bit stressful for some individual, but these things bounce back pretty quickly. Try making the room brighter...as bright as you can get it. I know somebody who kept a baby leaf turtle in her bed room with low-watt heat lamp and UVB, but one day it stopped eating. So she moved it to the room that was brighter and warmer where the rest of her animals were. It began to eat well after that.