OP, every fall - usually in August, I stop training. I take a month off the bike and do very little physical exercise. After 11 months of steady training and racing, I need the time off. My body is just worn out. I find that during that month off, I become very lazy and tired and really seem to enjoy doing nothing. It takes a bit of effort to start working out again.

Given you description of how much you were working out, I would not be surprised if you are experiencing something similar. You could have reached a point where your body was completely fatigued and is now crashing.

All that said, if you haven't been to the doctor in awhile, it's not a bad idea to go. When I was your age, I never went to the doctor. Now, due largely to my wife's constant reminders, I get my annual check up - just wait til you have to get your first prostate exam, FUN!