I have a cough I cant get rid of......read on?

I get a cold every year at the change of seasons and I end up with a cough I can't get rid of. Last year I had chest x-rays, extensive pulmonary function testing and I also saw an allergist, ENT, pulmonologist and a cardiologist all telling me there was nothing they could find wrong. I do have a history of stomach reflux but I havent had a problem with it and I take Prilosec regularly. I have it again this year and I am really on the verge of a breakdown. Im tired and by the end of the day I am beat. I have been taking anxiety medicine to relax me because I feel like crap. I want to feel better. HELP!?!?