It really depends on what type of whistleblower case you have. There is a difference between a whistleblower claim under federal law and a whistleblower claim under state law. Based on what you've said above, I'm assuming that you have a state law whistleblower claim. In other words, you were fired after objecting to or refusing to participate in illegal activity.
These are tough cases and there are a number of hurdles to clear, but if you were fired for refusing to engage in illegal conduct, then you should speak to another attorney and get a second opinion about your case.
My response to this question is a response to a hypothetical situation based on limited facts. I am not your attorney; you are not my client and we do not have an attorney-client relationship. If you need a lawyer, you should contact one in your area. If you would like to talk with me about your case, you can call my office.
I would check AVVO for attorneys in your area that handle employment litigation. I would also call your local county bar association. Your attorney might have simply wanted the case to see if he could get a quick fee from settlement, or something else might have come up to dissaude him from proceeding. In any event, you should contact an employment attorney to determine whether you have a viable basis for a claim against your former employer.
Check the webpage for the Florida Chapter of the National Employment Lawyers Association. All members focus on representation of employees.