Bactrim DS 800-160

I have an ear infection and sinus infection as well. My doctor gave me bactrim DS 800-160mg. Since I am highly sensitive to medications, I went on the internet and was surprised to hear all the horror stories about the side effects of this drug. I am scared to begin to take it. Can anyone tell me if I should be concerned about using this drug. I can easily call my doctor and have her change it. thanks