Have you had a checkup at the doctor lately?
When I turned 50 in 2007 I also lost all my get up and go. When 6 or 7 at night came I was shot for the day. I was use to 15 hour days and could not make 10 in the spring.
By mid summer I was pretty sick. I ended up in the ER one weekend and found to have CML. After a few months of treatments I was back to 14 hour days for the fall harvest.
They said I may have had CML for a year before I found out.
That was 5 years ago and still feeling good with daily Medicine. So far I am still in remission.
You might want to get a good checkup.