Clear water dripping out of my nose.

I am suffering from this since many years.my nose starts dripping clear fluid whenever i bend or if someone hits lightly on my nose or if the weather is extremely cold.if i have my left nose dripping then my left eye starts watering and left ear starts itching.it is nkt normal cold.its a clear watery fluid that dripps from my nose...and its irretating.i can taste it salty when i happen to swallow it.i have been told that i am suffering from cold since i was a kid.but now its getting worse.i need to carry big towels to blow because tissue papers are not enough.one physician told me that u might be allergic to dust.but i dont think so because i come in contact with lot of dust on my way to my office... Nothing happens that time.only if water enters my nose or if ac is right on top of my head or its extremely cold in the morning or if someone hits me or touches my nose,that is a time it happens ...please help