Abdominal pain with lower back pain and discomfort bowel movements?

i went to the doctor for reg check up had blood in my urine she gave me bactrim went back to the doctor o told them i was having abdominal pain no burning when i urinate i been going to the bathroom alot though and i have lower back pain he told me my back pain is because of my weight so i told him i have both front lower abdomen and lower back pain he didnt want to keep giving me meds so he sent me to get a sonogram of my kidneys and bladder my appt is monday but today when i got to the bathroom to p bowels i get a slight uncomfortable pain im not constipated this is the first time i have a sudden change in body if it doesn not improve i will be going to the er to see whats going on maybe it can be gas