What Causes Fatigue After Bacterial Pneumonia And How Long Does It Take To Cure?

I have had a bacterial pneumonia since Xmas (perhaps before), and have finished all my antibiotics, no longer having the violent coughing. It is going on 2 weeks and 5 days, and no more coughing, but extreme fatigue and shortness of breath with ordinary activities (doing the wash) exhaust me, difficulty walking the dog two blocks up the road etc. I have been sleeping long hours, and resting a lot. No appetite but force myself to eat solids, drink protein drinks, take a lot of vitamins, pro-biotics, etc....and drink plenty of liquids. I am normally a very fit 69 year old female, swimming strongly 3 x week for 50 minutes, going to the gym etc.. I am prone to allergy related asthma with weather changes and pollens and have been dealing with atrial fib successfully. This pneumonia came from nowhere as I was the picture of health before it hit. Should I be concerned that I am so tired? How long should this fatigue go on? I have a doctor whom I ve seen twice now, just wondering if you have any input. Thanks for you insight. terry