I Have Had A Persistant Cough And Conjestion For 7

I have had a persistant cough and conjestion for 7 weeks and is still not quite over. I seem to get this once or twice per year, and usually with part of the time having a very sore throat. Routine stuffdoesn't seem to work. Worse at bed time when i lie down. Had as chest x-ray and said lungs look okay. What is this.