Speak to your attorney about filing an initial complaint for child support.  In some circumstances you are able to ask for retroactive child support (which is support owed for a time period before the complaint is filed) along with prospective child support (which is support to be paid from the date of the filing of the complaint forward in time).  Be mindful if you have an agreement to pay child support in a Separation Agreement that has not been incorporated into a court order.  This Agreement could affect how you seek to obtain an initial child support order in court.  Please speak to your attorney about what this means and how this could affect your case.