Hello, My Name Is Joe. I Am Very Healthy,71 Years

Hello, my name is Joe. I am very healthy,71 years old, take no medications. For quite some time now I always feel tired or mildly fatigued. I get 8-9 hours sleep each night. My CBC results are always good with the exception of a low red blood cell count, which has always been the case for me. What do you think ?
YYYY@YYYY . Thank You