i have this problem often also. its just like your wife said. infact, i found that it was extremely worse when i smoked. as soon as i quit smoking, i quit coughing and clearing my throat all the time. sometimes ( mostly during the pollen seasons and other times when i am around allergens) i still do have to clear my throat a lot, and also find myself swallowing a lot because i feel like something is back there. it can get really annoying. it also does it when i get nervous, like i know i am about to talk to someone on the phone like a client or something. it is drainage though. you should either take an antihistamine or try to find your allergen and eliminate it.
did you ever have your tonsils or adenoids removed?