I am taking Cephalexin 500Mg twice a day for several days just as a precaution to avoid an infection from a sore on my ankle. I feel awful with diarrhea,tiredness and stomach upset. I am small a size 2 and think the dose is maybe too much?? Or there is something in it that doesn't agree with me. I have been gluten,dairy.sugar and gmo free for three years.