Hi Craig.
I sure can relate to your problem. I'm no Doctor put I will relate a few things to you.
I have the same disgusting problem with phlegm especially in the morning and sometimes it does continue throughout the day. However mind is probably due to years of smoking. Started around 13 now I'm going on 60. I did quit 3 years ago and even though these tough lungs show no obvious damage I think there must be some part in them that have weekend. The Doc. still thinks that this will clear in time. I doubt it but what the heck.
About 2 years ago I thought I had Laryngitis as every time I started to sing or talked to much I would loose some words as if this is what I had. But to make a long story short I finally got to a specialist (Montreal Canada) and she said that I had bowing of the vocal folds. Where by the folds would not close completely and air would pass through giving one the impression that laryngitis was the problem.
   She then injected a product (collagen I think.)to build up the fold. However this is not a permanent fix and after 6 to 8 months it wears off.
So three months ago I had two implants inserted in the folds. This is apparently a fairly new thing and with great results (In most cases). I'm still having problems but some days I can sing fairly well while others I can't carry a note in a piss pot. I go to a speech therapist and in the test she makes me do I see improvement and she is very happy. I'm still the one not satisfied.
What really frosts my nuts is that I had just put a Celtic band together when this all happened.
I asked the surgeon what caused this and I didn't like either of her answers.
1) If you live alone, go to work and your work involves very little communication resulting overall in very little use of your voice.
2) Age. The folds finally say. F....it. I'm tired. You abused me for years now I want to rest. My muscles are fagged out.

Unfortunately I fit in the second class. Curious?? Would you fit in one of these? If your a singer I doubt that your in the first example. Then again you may have a different problem altogether.
Go to Kendall's thread at the bottom and you may pick up some great advice.
I truly wish you the best. If your a young person then I truly advise you to get professional help and good professional help.
Beer

When I can't play I'll sing,
When I can't sing I'll whistle.
When the day comes I can't whistle no more,
I'll sit myself down and I'll listen.