Sounds like you entered a plea today as you state you are on probation. If so, it is basically too late to change that unless you file an application to withdraw plea and can show the plea was not voluntarily entered. If you test hot, you will violate your probation and can be sent to jail for violating probation.
Answers to AVVO questions are for general purposes only and do not establish an attorney-client relationship. This answer is not a substitute for legal advice and should not be relied upon without a full consultation with an attorney that can fully look at issues involved.