nausea and back pain are not common
symptoms of sinus problems, a
headache can be, but with these other
symptoms, its unlikely. you do need to see a dr and have multiple testing done, focusing on the abdominal region. theres a lot of stuff in there, leaving you many possibilities. kidney stones, infection, bowel problems, ulcers, gallbladder, etc, etc, etc. also, a kidney infection doesnt usually show up when checking for bladder infection, but it can work down to the bladder.