My 11 year old daughters had strep throat 2 weeks ago and was put on Amoxicillin for 10 days at the end of 10 days her throat was still hurting. I took her back to the pediatrician and she was still positive for strep. This time she was given Zithromax for 5 days. Now a week has passed and. she is starting with congestion, coughing and throat hurting again. She is otherwise a very health child. Please advise, is there something more serious going on?