So... reality time. There is no way I can train for a marathon until I figure out why I feel so miserable when running outside. Normally I would expect my conditioning to improve with time instead of getting worse. But today I ran at the college track -- a nice flat surface, easy to run on -- and I had exactly the same problems I have in the neighborhood. I hadn't even gone half a lap before I felt exhausted and started gasping. I made it one mile, and then coughed for an hour afterward with burning lungs.
I suspect that I have exercise induced asthma, or exercise induced bronchospasms. The symptoms seem to match. So I guess I'd better make an appointment and have this checked out. Maybe I'll get lucky and they'll tell me I'm just out of shape or lazy.
But in the meantime, I will have to adjust my goals. I still want to run a marathon, but depending on what is causing this problem, it might take me two years instead of one... Ugghh. I don't even want to think of it!!!!