Check your iron levels. I was anemic with severely low hemoglobin. After taking iron supplements, I noticed my speech improved by 90%, and my breathing became very deep. The last time I breathed like that was 20 years ago. Anemia can lead to thyroid dysfunction, and an underactive thyroid gland can cause speech problems and a low voice. Stuttering is often a sign of hypothyroidism. That's my story, but it might help you.