Under the statute, you must have "successfully completed" your sentence before you apply for expungement. You must have been under the age of twenty-five on the date of the offense in order to be eligible. For more on expungement, see: http://www.jensendefense.com/hereshow/expungeyourrecord.html
This answer is for informational purposes only. By answering this question, no attorney/client relationship is created. Although the legal information is accurate, it may not be appropriate for your situation. The best way to handle any legal problem is to seek the advice of an attorney.
If the trial court addressed the question at the time of sentencing, or agreed to revisit the issue, the timeline should be spelled out in your judgment of conviction. If the question was not addressed at the time of sentencing, you may not be eligible under current law without some serious post-conviction work.
You can use CCAP to check the abbreviated court minutes from your sentencing if you did not keep your copy of the judgment of conviction.
This answer is provided for general information only. No legal advice can be given without a consult as to the specifics of the case.
Additionally, most felonies cannot be expunged, only those few that are specifically designated by statute. If you were convicted of a felony that is not subject to being expunged, your only recourse is for a pardon. However, under Governor Walker's term in office, no pardons have been granted, to my knowledge.