Son now living with me

My ex kicked my son out of her house over a month ago. He is now living with me and now I need to get the correct paperwork filed and signed so I can get this behind me. Can anyone tell me the correct forms I need to complete to:
End the child support I am currently paying my ex wife since my son was living with her on a full time basis as of our divorce and signed in our judgement.
To now request child support from my ex wife since he is now living with me on a fulltime basis.
How to get the order modified so it shows I am the primary caregiver.

You must make a motion with the court to modify child support based on the fact that your son is now living with you.

I did file the correct motion but it seems at least in Johnston County you must file a motion and notice of hearing to change custody-visitation of you cannot have the motion to modify child suppport heard. I have no made two child support payments and yet my son lives with me. The system does not work and as always you have to spend money that you do not have to even attempt to get justice. Just a real shame that at the end of the day the children get hurt but truthfully I do not think anyone really cares. Wrong motion filed. Oh well I will just keep trying.