Hi, there. Did you take his temperature? If he's running a fever, then it's probably the flu and the only thing that really helps that is sleep, liquids, and fever reducer such as Advil, Tylenol. I've felt that way before and could have sworn I had a fever, but when I took my temperature, it was normal. So it's probably just viral and will pass in a few days if his symptoms don't get worse. If they get worse or don't stop within a few days, it might be good to call the doctor.