There are not enough facts here to provide a meaningful answer. I suggest contacting an attorney to review the facts and develop a strategy. Many reputable attorneys offer a free consultation. I suggest meeting with at least one soon while the facts are still fresh in your mind. Not only for that reason, but by contacting an attorney early you have an opportunity to confer with the prosecution beforehand with the possibility of having the charges rejected altogether before the court date.
The response above is not intended as legal advice since it’s impracticable to provide thorough, accurate advice based upon the query without additional details. It is highly recommended that one should seek advice from a criminal defense attorney licensed in your jurisdiction by setting up a confidential meeting. Moreover, this response does not constitute the creation of an attorney-client relationship since this message is not a confidential communication because it was posted on a public website, thereby publicly disclosing the information, which is another reason to setup a confidential meeting with an attorney.
I agree with my colleagues that more information would be required including what the sentences or outcomes on each prior case was. Based on what you say, the new petty theft would not get charged as a felony petty theft with priors because you need three theft related priors to trigger that rule. Consult with a local attorney to review your options. Good luck.
This will probably be filed as a felony petty theft with a prior PC 666. If you are on probation or parole this could be serious as far as jail time so make sure you seek legal counsel.