I Am Female , 76 Years Of Age. I Have

I am female , 76 years of age. I have been having trouble breaking out into sweats just doing simple things like dishes or cooking. I get a real weak feeling from it and it only last the most 15 or 20 minutes. I also am having trouble breathing when I am lying flat on back or just reclining in recliner. I have been using some oxygen and it seems to help some.