Treatable symptoms and conditions

My 17 year old son was diagnosed with MRSA after getting an injury on his knee from playing basketball.After the first does he had a loss of appetite, fatigue, nauseous and severe headache. By the third day he got a fever, chills, neck stiffness and a feeling of doom. We went to the ER because his blood had not been cultured and we were afraid of sepsis in the blood. The ER doctor said it was most likely viral and sent him home. The next night he had a fever of 103, sore throat, trouble swallowing, sun burnt look, swollen eyes and cracked swollen lips.The next day we went to the urgent care and they tested him for mono, strep and the flu...(all negative). He felt awful and was so tired and feverish. The next morning he woke up with a severe rash and itching all over his body and his skin looked like it was scalded. His blood culture came back negative for bacteria and his wound has healed. I have taken him off of this drug Bactrim. This is his first day. His rash is better and his fever was down for a little while. It is 101 tonight and he just feel so tired and achy. I know it will take time for this to get out of his system. Meanwhile he is missing school and is getting depressed because he feels like he will never get better. If someone told me that fever and chills were a side effect from this drug I would not have been so worried that he could die of a blood infection. Ask lots of questions or google this site before taking a new drug.