When you plead guilty the judge asks if you are acting freely and voluntarily, and you give up your constitutional rights. Since you had an attorney at your plea, it will be extremely difficult to have your plea set aside. Good Luck.
I'm not sure that there is a valid grounds for an appeal in your case and a pro bono appeals attorney is hard to come by. I have provided a link to the Detroit Bar Association, try contacting them to see if they know of anyone who could help you.
Disclaimer: Posted answers do not constitute an attorney-client relationship and are based on the general information available in the question posting. Always contact an attorney in your geographical area with the specific details of your case before taking any action.
Try contacting all the law schools in Michigan and ask them if they have a criminal defense clinic. I know that the University of Detroit Mercy has a criminal defense clinic. If a law school accepts your case, then a law student under the supervision of a law professor can handle your case on a pro bono basis.
This is general information and not legal advise. This communication does not create a lawyer-client relationship.