Hi, I Was Away At A Training For A Couple

Hi, I was away at a training for a couple of week and since last Monday I have experienced waves of sweating, followed by chills and fatigue. I'm 40 and generally pretty active. I feel icky but not really sick most of the time. I tend to get tired in the afternoon and end up taking naps. Do you have any thoughts on what might be going on?
Thank you, kristen