I can understand your concern.
I have gone through your history in which you have mentioned that you are working as a teacher.
Yes, most likely you are suffering from vocal nodules which are also called the teacher,s nodules which may be causing the pain you have and they also cause a change in the voice quality.
It's common in people who do a lot of voice abuse like singers, teachers and other such professionals.
Give your voice some rest and speak little softly because the louder you speak, the more your condition will worsen.
You need to consult a ENT specialist in person regarding this and get it checked out for further evaluation and management.
Dr. Anil Kumar Jain.