I Will Be 50 Non Smoker This Month And Gor

I will be 50 non smoker this month and gor about a year i cant go up a fligbt of stairs say 20 steps or doing yard work mininal work with out getting out of breath and need to rest i get shakey to. I also cough through out the day so bad i choke and cant catch my breath like i smoked two packs of smokes. My doctor put me on hear mo itor for 24hrs nothing eco on my heart nothing breathing tests nothing . She doesnt know wht else to do any suggestions.