You will have to argue that your illness prevented you from knowingly, voluntarily, and intelligently pleading guilty. You'll need expert witnesses, others who saw you in court or very soon before or after pleading. The judge will think back to the plea and decide if you were incompetant to plead guilty. Keep in mind, if you didn't look bad enough to cause the judge to inquire into your health, the judge will likely not find you incompetant now.
You can also argue that your plea was involuntary because you felt pressured. However, it is extremely hard to prove that you were pressured. You have to prove that the state or some outside person pressured you. Feeling pressured by the situation or by having few choices, none of which you like, is not sufficient grounds to withdraw a gp. The one thing you have going for you is that you haven't been sentenced yet. It's a little easier to withdraw a plea before sentencing.
Allowing withdrawal is largely a matter of judicial discretion. If the judge denies your motion, you won't win on appeal.
It's a longshot, but it may be your only shot, so go ahead and try. Just don't get your hopes up. It will be expensive.
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This is not legal advice and you are not my client. Double check everything with your own attorney and your state's laws.
