Please help.. I really need your advice here...

I have a pending case in MTCC for Alarms and Scandal and Drunkeness. During prelim, I pleaded not guilty and I had a law firm who handles my case. I filed a counter affidavit stating that everything in the the information that was filed against me is not true. After 3 times appearing in the court, my lawyers decided to withdraw as counsels for my case so currently, I'm considering for a change of plea and to plead guilty for the charges that they filed against me because I'm really so busy with my job and I don't have time to look for another lawyer. My questions are: If I plead guilty, can they file perjury case against me citing the statements that I have made in my counter affidavit? Can they use my change of plead as basis for filing a perjury case? Are there any supreme court decided cases in the past which is similar to this? Please enlighten me on these questions. Thanks in advance