Family Law Questions? Ask a Family Lawyer Online.
Do you mean that you are paying child support?
If your son is living with you, you can petition the court to terminate the support order, or even ask for an order of support from the mother. If the courts are not made aware of the living arrangements or there is no request to terminate support, they will not do so on their own. You will need to be proactive in asking the court to terminate the support that you pay to the mother based on the fact that the child is now living with you and you are supporting the child in that way.
Regarding custody, it is possible that you can petition the court for an award of custody, particularly given that the child has been living with you and the mother has been abusing drugs and alcohol. When making these types of determinations, the court must consider the best interests of the child, and exposing a child to these elements is normally not considered to be in the best interests of the child.
I hope this answers your question. Please let me know if you have any follow-up questions.