Why do I have this type of phlegm?

I have a really sore throat, fo rthe past three days actually. My voice inst hoarse, it just hurts to swallow. I am constantly producing this thick saliva, and I have to spit it out. It is clear with a lot of bubbles. In the morning, I have this really think mucus come from the back of my nose/throat and I have to cough it up and spit it out. It is yellow with rusty spots? I dont have a stuffy nose or sneezing. What could I have? what is the best was to solve it? Thanks