My voice is shaky and it's embarrassing! I'm not nervous, but my voice gives others the wrong impression! What can I take or do?

Voice therapist. You may just have some poor vocal habits... Short breaths to speak rather than long breaths, etc. You may want to see a speech pathologist/voice therapist or an ENT who specializes in voice (laryngologist).
ENT and Neurological. Information given is scant. You need ENT and neurological consultations.