How to get rid of mucus from the back of your throat and nose?

i have had a cold, or maybe it was hay fever im not too sure. and i have been taking hay fever tablets. i have had a really blocked nose but today i have had mucus at the back of my throat, and i cant get rid of it. it feels as though its dribbling down the back of my throat. i have blown my nose, and still cant get rid of it. HELP PLEASE!