Criminal Law Questions? Ask a Criminal Lawyer.
I'm sorry to hear about your situation. Because the charge is first degree petit theft, which is a first degree misdemeanor carrying up to 1 year in jail and/or a fine of $1000, it is a good idea to get a lawyer to represent you to negotiate the best outcome possible (particularly since you've already confessed). If you can't afford a lawyer, you may want to see if you qualify for the public defender.
The good news is that it is highly unlikely that you would get jail time for a first shoplifting offense. However, you don't want to get a criminal record because of one mistake. Fortunately many counties offer programs like deferred prosecution and pretrial diversion programs. These programs involve a period of probation (usually 6 months to a year) and sometimes other conditions (like community service). If you complete the program successfully, then the charge is basically dismissed, which keeps the conviction off of your record. You can try to negotiate for this directly with the prosecutor yourself when you have your court date, but many people prefer to have an attorney there to handle it and to make the arguments on your behalf.