This is Dr. David
the throat swab didn't show a bacterial infection.
the ENT doctor looked down there and saw acid reflux damage to the throat.
you have had a history of acid reflux damage.
your throat and esophagus nerves could be damaged from repeated acid reflux so you may not even been feeling the acid reflux anymore
taking antibiotic can help decrease inflammation in your body and that could be why after a few tablets your voice got better.
but you need to work on decreasing this acid reflux.
avoid fatty foods, alcohol, tomato sauces, fried foods, large meals, eating close to bed time, sodas,
and you need stomach acid blockers to decrease stomach acid.
I don't think the clarithromycin is the answer to your throat and voice issues.
you may need to sleep on an incline foam wedge to help let gravity keep stomach acid down in your stomach.
weight loss and increased exercise and improved core muscle strength can help keep stomach acid down in your stomach as well.
let me know if you have questions.