You would need to file for child support modification/review based on your income, the income of the mother, other exception that may apply such as having other children in you care, being a custodial parent more than 35% of times, health care payments/credits, undue hardship, etc.
Review closely the section on DC Child Support in our site and also the link to DC Child Support Guidelines: Familylawdc.com.
You should consult an experienced DC child support lawyer. This response does not constitute/create an attorney-client relationship. Moreover, this answer is informational only and cannot be construed as a legal advise.