What Causes UTI While On Nitrofurantoin For Abdominal Pain?

I have been feeling pain in my lower abdomen since yesterday - i traveled all day on an airplane and thought maybe i was just constipated or trapped gas from sitting all day - but i went to bathroom two times and that was not it the pain has gotten worse now i feel feverish and can barely walk- i could not sleep i have a prescription for nitrofurantoin mono/mac. I seem to get urinary track infections a lot - i tried one when in got home and felt no relief so it doesn t feel bladder or urinary track related even though i am feeling pain - and my urine is clear. the pain is getting worse instead of better the only thing i have done differently in the last few days is i took for two days injections of HCG that i got to start a weight loss program. But i didn f feel any side effects after the shots?