What happens to mucus if you can't cough it all out?

I have been to 4 doctors this week with a bad case of either bronchitis or possibly pneumonia. They sent me home with antibiotics and an inhaler and said to drink lots of water & take Mucinex. I have been out of work for 4 days now, sitting home next to a trash can coughing up junk. I'm at a point now where if I cough, there's a vibration in my chest like mucus is there, but nothing's coming up. What will happen if it never comes up? Does the body eventually take care of it, or do I need to force myself to keep coughing? I'm physically exhausted from coughing :(