UTI symptoms but negative result?

Patient: Hi, I’ve been having trouble with what I thought was a UTI. About a week and a half ago, I started to get the urge to pee continuously, every time I would go, it would not satisfy. I also had a horrible bloating sensation in my lower abdomen, not really pain but perhaps an ache. I went to the doctor, he told me I had an overractive bladder and gave me Betmiga to take. After a few days, I felt worse, I was on the toilet almost constantly, so returned to the doctor and he said it must be an infection (although he had taken no urine test at this point). So I was then given the antibiotic Norfloxacine, and after 2 days I felt great, I was feeling completely normal but then the following day, I started to notice twinges in my lower abdomen and by that evening, the urge to pee had returned. Back to the doctor the next day, he finally sent away a urine sample to be tested but now it’s come back as a negative, no bacteria found. so I’m at a loss what to do. I’ve been drinking only water, and loads of it, I’ve cut out caffeine, sugar, anything citric for over a week now. I’m just not sure what’s going on. Could you help me please? I’d really appreciate it.

Symptoms: Urge to urinate continuously, bloating

Doctor: