Melissa Kim M.S., CCC-SLP replies...
If an Ear, Nose, and Throat physician has determined that your larynx and vocal cords are healthy after a thorough evaluation, I would suspect that there is at least a component of a functional voice disorder (a problem with the way in which you are using the voice). To address a functional voice disorder, voice therapy with a speech pathologist who specializes in the treatment of voice disorders can be helpful. He/ she will be able to prescribe specific exercises to address specific concerns.
Thyroplasty is a procedure done most often to correct a vocal cord paralysis. If you are still uncertain as to a diagnosis, which I suspect, I would suggest that you seek out a laryngologist (an Ear, Nose, and Throat physician who specializes in the treatment of voice disorders) for an evaluation and treatment recommendations.
Good luck to you!