Thanks to everyone for their input. Just an update, I borrowed my brother's stray inhaler (no $$ to go to the doctor just this moment) for my run this evening. I took a puff 10 minutes before, and one midway through the run. I also tried to time my breath (this has always been impossible for me in the past, due to my incredible difficulty breathing/chest pain).

Wow!! Is this what it's supposed to feel like!? I don't know if it's the inhaler or the breathing (maybe the former caused the latter?) but I didn't get out of breath AT ALL and my chest didn't hurt a BIT!

Now I feel like I can finally work on my endurance. Before, I'd always hit the wall of my troubled breathing and couldn't break through. But now maybe I can actually be a runner!!

I'm going to see the doctor as soon as I pay off the last bill I owe him, but I think I can be reasonable sure this is exercise induced asthma, right?