Re: can't breathe--pulmonologist says its asthma, I think otherwise.

 as a kid I was diagnosed with asthma, then it "went away" or whatever,

This is common.  Children will generally outgrow their asthma around the age of 5 as the adrenals mature provided they don't atrophy their adrenals with steroidal inhalers:

http://curezone.org/forums/fm.asp?i=1443971#i

and then for at least the past 5 or 6 years I've had breathing problems that progressively became worse and worse, which of course I figured was due to the fact that I had started and continued to smoke cigarettes (and for a time I smoked weed).

it feels like my chest is caving in. like my lungs don't want to expand all the way. my ribs hurt in the front and back when I take a breath. sometimes my lungs feel very itchy or burning. it's always worse in the morning. I constantly feel like I'm drowning in mucus, always able to cough some up when I try. there's an extreme tightness in my chest, and I just always feel like I'm not getting enough air. sometimes it sort of feels like only my left lung is expanding when I take a breath, though I've had chest xrays and they've never shown anything wrong structurally. but I can't help but be paranoid because no medications have helped me.

I have an albuterol inhaler which does nothing for me, I was put on singulair which made me go crazy, I had taken oral steroids and some sort of powder inhaler last summer, neither of which did anything. the latest doctor gave me advair, but I read up on all of the warnings about it and couldn't bring myself to take it.

I'm terrified that I have emphysema or something horrible.

The mucus in the lungs does not sound like asthma or emphysema.  It is more likely chronic bronchitis unless the mucus is from sinus drainage.

Are you overweight, or really thin?  Skin have a bluish or pinkish cast?  Is your chest kind of "barrel" shaped?

what I don't understand is up until a few weeks ago I was typically able to do 30 minutes of intense cardio without much trouble at all. now I can't even make it 10 minutes without freaking out.

I do feel the need to mention that I have severe (and I mean crippling to the point where I have no life, don't leave my house, and can no longer function on ANY level) anxiety and panic attacks.

Lack of oxygen can lead to a lactate build up, which is an anxiety trigger:

http://curezone.org/forums/fm.asp?i=1662316#i

and it's almost always triggered by my breathing. problem is, I don't know if I legitimately can't breathe and that's why I get anxious, or if I'm just anxious and that's why I can't breathe.