Hello,
Thanks for the query to H.C.M. Forum.
No doubt you run so many marathons in past ,but this is not granted that you are free from disease at now.
As your age is 41 years old and the level of
estrogen starts diminishing .
2nd obvious reason is weight gain .
The most important thing for you is breathlessness due to exertion ( as you stated that when you walk upstairs ) so these type of symptoms may be due to
1 Decrease in stamina as you you gained 12 lbs .
2
Asthma ,if you have any
allergy type symptoms or sign , which you didn't mention in your query.
3 Due to involvement of heart .
As all these conditions are related to each other more or less , so get in E C HO . pulmonary function test and last of all about stamina either reduce weight or try to increase stamina by regular exercises.
Consult a physician and get confirmation that you have not any disease.
Good luck.
Dr. HET