Depending on the dates ( your arrest, your plea/sentencing, date officer was discharged, etc.) you MAY have a ground to revisit your plea. This is a difficult undertaking to get a judge to allow you to withdraw your plea. Time is not your friend. Act immediately in seeing an attorney to review the file.
I am trying to give you a general answer to your question. We do not have an attorney-client relationship by this response on the avvo website. I have not been retained to represent you. I am licensed to practice law in Kentucky and in federal court in this state and the Southern District of Indiana. You need to seek legal advice from an attorney licensed to practice in your area..
I agree with my knowledgeable colleagues and wish to add one thing. Having a legitimate chance to accomplish something favorable WILL require the assistance of counsel. Hopefully your financial situation has improved; handling it yourself strikes me as a waste of time.