Suggest Remedy For Discomfort From Thick Hard Phlegm In The Throat

Hello. I have this sticky mucus, a glue-like white phlegm in my throat for weeks already and I can barely have a good night sleep because of the discomfort. I have already taken antihistamine per advise of my EENT but I had a dry mouth instead and it didn't remove the phlegm in my throat. What shall I do? Am, taking PPI for my hyperacidity (omepron). Please help. By the way, the phleghm doesn't come out even if I try to spit it through throat clearing.