Get a lawyer. File a petition to modify. Ask for emergency orders, i.e. attachment of the child, then temporary orders. You'll never get it done without a lawyer.
I am not intending this to be legal advice, because I don't know the particulars of your situation. Call me if you would like to discuss this or other isues.
I agree with Attorney Moore. You need to get a petition for modification in ASAP before she moves again or your child is in further danger. Talk to a local attorney about filing a modification, getting attachment, and putting in motions for a drug test and some new temporary orders.
You should file to modify custody. Always use a lawyer when a child is at risk, like here.
This answer is intended for informational and educational purposes only and should not be considered legal advice nor forming the attorney client relationship. This attorney is licensed in Texas.