How can i stop my sinuses from draining down my throat?

ok for the last ten years or so (by the way im 24) my sinuses have been running all day ever day. ive tried different allergy meds and claritin so for the most part they don't work, the drainage doesn't really go to my nose it just goes down my throat all day so if i don't blow my nose like every 2 minutes i feel sick. i don't know what to do. ive had an allergy test and other than roach dander, down feathers, and wheat pollen im not really allergic to anything. no matter what time of year it is or place im at it happens. i was in the navy for a few years and it still happened. ive lived in indiana, georgia, Connecticut, florida, new hampshire, and virginia and it wont stop its driving me nuts and being the guy at work who blows his nose all day long a hundred times is getting old im tired of the questions and looks can anyone help??????