Keflex and muscle spasams

I have been taking Keflex for the past two days, one 500mg dose every 12 hours, and I only had 3 doses total when I started having severe reactions. I had very sharp abdominal pain and cramping, then felt very hot, then very cold, and began to shiver uncontrollably, my hands and legs got tingly and then my legs began to have muscle spasams. These symptoms lasted for about 3 hours and today (next morning) they are better for the most part but I still have abdominal pain. I don't think I will take this drug again.