Hi bunnaaay5! You have what is called silent GERD, or LPR. This means that you don't necessarily feel heartburn in your upper stomach but you are refluxing and the acid from your stomach is attacking your oesophagus and vocal chords. Mucus is produced by your body as a protective mechanism to coat your throat and stop any burning.
It is very, very difficult to treat. Because the acid is attacking your sensitive throat area, it needs to be wiped out all the time, not just for 24 hrs, so unless the tablets are taken twice a day and have a long enough duration to cover 'all the time' then even a small amount of acid is going to affect you and the mucus will still be produced!
The symptoms you are getting with those tablets are side effects and can be very unpleasant. You need to go back to your Dr and get another similar type of medication that will not affect you , maybe Omaprazole. You just need to find one that suits.
Also look at your diet. There are certain things that will make the mucus worse, like chocolate, coffee, onions, tomatoes, garlic, chilli, milk. Trial and error will let you know which ones effect you.
Good luck!