Oh I have been having headaches too, only been on the Cephalexain 2 days, I get a very very upset nauseaous stomach feeling like I need to vomit, go from being comfortable to feeling very very flushed and woozy, found laying down and sleeping is the only thing that makes these feelings go away, of course I am on a 10-day course and I dont think my boss will like me laying down and sleeping! This sucks!