Hey there,
This is Kitt.............do you wheeze at all when you feel short of breath? The is an exercise induced asthma that will cause people to feel short of breath. I have a friend that bikes and has for years an all of a sudden developed the exercised induced asthma............she now uses an inhaler prior to biking her 50 miles a day...............
I am lucky to walk 50 steps a day.........lol.
Good luck and keep us posted.
Kitt