I Seem To Have A Sinus Infection/cold Of Some Sort

I seem to have a sinus infection/cold of some sort that is causing my sore throat because of constant drainage down the back of my throat, along with a cough which only comes when I try to lay down. I feel terrible - like a have a bad head cold, my neck aches however - but no runny nose, nasal drip, etc. Just the throat thing for about 3 weeks. Would a course of clindamycin help get rid of this weird cold.