I took an antibiotic for 5 days for a UTI last week. I had a mild cold during that time and seemed to be getting better. Two days later, during my last day of antibiotics, my cold symptoms got worse. It was now been a week and I still feel just awful. I have nasal congestion and thick mucus, a slight cough, mild fever, aches and chills. Did I destroy my immune system with the antibiotics? What can I do to get better? This is ruining my summer off!