Do I need to pay child support if I have mentioned not to have this child while my ex-girl-friend pregnant few years ago? She said that she would take care by herself and this child after baby born. Now the child is 5 years old, Can I have right to see him?

If you fathered the child you have both the right to see that child AND the responsibility to support it.

The fact that you told her not to have the child will have no bearing wither your rights or responsibilities.