Hello and Welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice. Bactrim is a combination pill of sulfonamide group containing sulfamethoxazole and trimethoprim. Its use is sometimes associated with gastrointestinal disturbances like nausea. However, what worries me is the shortness of breath you are experiencing. We should focus in understanding that. So, it might be related to the primary diagnosis for which you were prescribed Bactrim before admitting it is side effect. I advise to consult with your doctor if the symptoms will continue without improvement. Hope I have answered your query. Let me know if I can assist you further.