As a public employee, you can be disciplined or fired if your speech negatively impacts the integrity or functions of your employer or adversely affects morale. This is especially the case if your speech is a part of your official job duties.
But if you are speaking as a private citizen and regarding a matter of public concern, the First Amendment should protect your speech.
Determining whether or not your speech was a matter of public concern can be interpreted in different ways. This is why it is crucial to have an attorney who is able to prove the facts of your case and help you determine whether your speech will be protected by the First Amendment, against retaliation.