Sulfamethoxazole First Few Days, Upset Stomach, Difficulty Breathing, Meds, Nausea

My boyfriend starting taking this 10 days ago for Bronchitis and Tonsillitis. He was prescribed two a day for 10 days.
Before he started taking the medicine he had already been vomiting for a day before being prescribed to it. He continued vomiting for the first few days after and I assumed it was not from the medicine cuz he had already been vomiting before. A few days into the meds he was not getting better and only getting worse and got a fever. I took him to the ER and the doc said to keep taking the medicine and he would give him anti nausea meds. Even after taking the anti nausea/vomiting meds.. he continued vomiting. The vomiting eventually stops after a few days and then from there on out he still was not getting better. He complained about difficulty breathing and he can hardly eat anything and is coughing constantly. He said his throat feels like its an 1/2 inch wide and he chokes when he trys to eat something that is solid. He has been having severe neck cramps, headaches and upset stomach.
Finally on his very last day taking sulfameth he came to my house and i noticed his skin looked red. 20 minutes taker he had rashes and hives all over his body.
I don't know how often this medicine is prescribed or maybe people only write reviews when they have a bad reaction to it but from what it seems I would stay away from this medicine unless you know for sure you are not allergic to it.