Wow, Im glad I found this site. I was prescribed Bactrim last week for a sinus infection. The 1st day I took it I felt horrible nausea, and had no energy whatsoever. Ive had horrible back pain all week, which I had not thought was related to this as well. My throat has been hurting, I was about to go for a strep test. I cant believe these are all most likely from the medication. I have 3 days to go on it. Im going to call my doctor in the morning and see if I should stop taking it.