The disposition, charge, and all records related to your arrest and/or citation are eligible to be expunged after three years from the date of disposition or discharge of your probation, whichever is later. However, you write that the "conviction continues to show up on background checks." Please know that when you received probation before judgment (PBJ), you were NOT convicted. In fact, you had to waive your right to appeal in order to receive the PBJ-- that is because appeals can only arise from "guilty" dispositions. You were not convicted, nor should you indicate that to potential employers. They will see the PBJ disposition, and are entitled to make their own judgments therefrom. But help your own cause and hold yourself out affirmatively as someone who has NOT been convicted.
Here is a link to a guide on expungements:
You are eligible for expungement three years after probation was granted or discharged whichever is later. There are other requirements for eligibility for expungements as well. You should either contact the attorney that handled your case or consult with an attorney to determine your eligibility for expungement.