Can't breathe, lots of drainage and phlegm, constantly coughing it up....help?

[AndeeAndersen]

For the past couple of years I've had problems coughing up mucus, but doctors have never found anything wrong when I bring it up and it seems to get brushed aside. Now it's gotten much worse, I'm short of breath a lot and find it hard to swallow. I saw a doctor about it a month or two ago and it was the same spiel, nothing wrong. I'm sick of wasting money on a medical system that doesn't care and will charge me hundreds of dollars for no results. I've decided to see a specialist and am thinking pulmonologist.

I was diagnosed with asthma when I was little, but have not had issues for years. I used to be able to swallow pills without water, but now even teeny tiny ones (my birth control) are hard to swallow (they're smaller than my pinky fingernail). I constantly cough up phlegm/mucus, though I've tried not too throughout the day, it's kind of gross and embarrassing. But I started to cough it up so much that I just started to spit in an empty water bottle instead of having used tissues everywhere. I drive two hours a day, and after a couple days I have a fair amount of the bottle filled.  I also love to sing, but currently can't even hardly make it through a song all the way without having to clear my throat.
It doesn't hurt at all, I just occasionally can't breathe and can feel the mucus clinging at the back of my throat and nasal passage. I cough to get rid of the mucus, sometimes trying to the point of feeling like I'm going to throw up.
Anyone else have something like this? Or suggestions of what it might be? What type of specialist to see? Things I might have them look for? Any help is appreciated.