I'll say what everyone else is saying, and add "are you keeping up on your liquids, drinking enough water?".
My wife keeps getting on my case that sometimes the lack of sputum not coming up, or is very hard has to do with the lack of water in the body.
Also, sometimes when having a coughing fit, trying to at least sip a little water may help to control the cough. Though when I had coughed up blood, I stopped the nebs for a few days, but had oral meds that I still took.
Hope things get better for you.