Sore throat and sinus drainage?

hey i have a little bit of a irritated throat. and i am also having some nasal drainage in the bac of my throat that is really annoying me. i can not seem to get it to stop. i cant blow it out or cough it out. but i can feel it draining.i took to mucinex and they have not really helped. what do you suggest i do? i think it may be allergies