I was prescribed Keflex 500mg to take twice a day for strep throa...

I was prescribed Keflex 500mg to take twice a day for strep throat. Since I started this medication I also came down with a cough, nasal congestion and I am soooo tired! I cant stay awake! I also have had problems with bowel movements. I took magnesium sulfate to try and loosen things up. It took two days before I finally had a bowel movement... very painful and bleeding! I don't know if the Keflex has caused the Castro symptoms or the terrible feeling of being tired all the time but it has been miserable! I have had a mild headache also, but nothing I cant live with. Just wondering if I should stop the medication? I started this on Wednesday of last week. It is now Monday.