Can you stop support payments after a negative paternity result but i signed an acknowledgement of paternity

If there is a child support order from the court, you can not just stop paying. You can file a modification petition for downward modification of the child support. If the mother is in agreement with you stopping the child support payments, I would still go to court and get it done legally, otherwise, the back payments would accrue and the court would issue a judgement against you. The answering of this question does not form an attorney-client relationship.