Can anyone tell me why when I exercise I feel achy afterwards? Not achy like sore muscles, but achy like the flu?

Whenever I exercise, I feel like I have the flu afterwards. I am achy all over, so bad that even my skin hurts. My joints hurt, my head hurts, I get the chills, and sometimes even run a fever. I have done this since I was a kid. My mom used to accuse me of doing it on purpose to ruin anything fun she had planned for us. As if I can purposely get a fever! The exercise doesn't even have to be that strenuous. Something like walking around the mall makes it happen. Has anyone heard of this, or known anyone else it happens to?