Presently, I have several assignments that involves public speaking. As a Lecturer, I speak to my students every day of the week. As a trainer for two rural development organisations, I also speaks to people regularly. Additionally, I'm a preacher of the gospel and my assignment in the church involves speaking to the congregants either in small or large groups from time to time.
My issue is that since January this year, I have been having issues with my voice. I had cough around early to mid January and got it treated, at this time, the cough affected my voice but what I noticed is that the voice issue didn't go even after the cough have been successfully treated. Now each time I speak to people, my voice will get cracked within 20 - 25 minutes of speaking and before long it'll be ceasing. I stopped taking cold water and other drinks but this hasn't helped. I really need advise on what to do.

learn how to speak properly and not shout when speaking to groups.... maybe invest in better microphones and/or megaphones