Are you still living with his dad? Do the three of you live together? Are you divorced? For you to get just the child tax credit with no Earned Income or child care credit, you had to say the child did not live with you for the full year and that the other parent was allowing you to claim the child this year.
If you are living together with the other parent and the child, you need to remove the child from your return completely, as only one parent can claim anything to do with the child.
The part about your other son was cut off so you'd have to come back add more in the comments about him.
