Chronic sore throat

I've suffered with sore throats for years and when I finished the doctors for the first time about it the GP wasn't worried and said some people just suffer with them. For the last 6 months I'm waking up with sore throat and by the time I go to sleep I still have it. I drink lots of water all the time and always have throat sweets but doesn't help. It's making me feel rubbish and I don't know what to do. When I look in my throats I can't see anything, although my tounge is always a yellow colour. Someone told me that it could be because I sleep with my mouth open? But can that really cause my throat to be that bad. Any advice would be much appreciated 

Maybe allergies. I think if it was serious you would have other symptoms such as weight loss..sleeping with mouth open does cause a dry throat however. Does the throat feel better after drinking fluid?

Yes, dryness is a possibility.  Others would include but not be limited to allergies, GERD, and candidiasis (thrush).  You might want to ask you doctor about those possibilities as well.