It is not illegal for a patient to go to multiple doctors and pharmacies. Although it should be when it is obvious fraud.
In Washington State (not DC) we have the
Washington State Prescription Monitoring Program
The Prescription Monitoring Program (Prescription Review) is a patient safety tool. Practitioners have access to the information before they prescribe or dispense drugs. The information provided allows a practitioner to look for duplicate prescribing, misuse, drug interactions, and other potential concerns. By having this information available before prescribing or dispensing, a practitioner can provide improved care to their patients.
Providers have to establish an account in order to get access. It became effective in January 2012.
However, it is considered a felony when a patient alters a prescription and you would contact your local authorities.
Perhaps your state has a similar program.