My son is 13 years old, two weeks ago he woke up with vomiting/fever/ chills, that went on for 2 days, then he was better then two days later, he was running a fever again and weak. Then he starting having chills again, high fever, chest hurt, head hurt, dizzy and extremely weak. Took him to doctor 4 days ago doctor said he had flu, they tested him for the flu but it came back negative. Doctor gave him an antibotic, just incase he wasn t better in a couple of days, so I had the antibotic filled 2 days ago and he has been taking it. He still looks really pale, and has a low grade fever in the afternoons and at night, and yesterday wakes up and can bairly walk saying his legs hurt really bad, and he is still complaining of his legs hurting today. Should he go back to doctor? Or is this something to do with the flu? Thanks