Mystery bladder problem. UTI symptoms but no UTI, could it be an STD?

[Azariah888]

In May I noticed I was having to urinate more frequently even when I hadn't drank anything. It lasted for a few weeks and I started getting slight pelvic and back pain so I went to urgent care assuming it was a uti. They said I didn't have a uti but put me on antibiotics and told me to make an appointment with a urologist. He said there were trace amounts of white blood cells but no bacteria cultured on it. My symptoms started going away right before the appointment and after that I was fine and urinating normally. About a month later I started having pelvic pressure, back pain and cramping and burning with urination, so I went back to the urologist. This time there were moderate white blood cells and sent in for a culture again. The culture was negative so he sent me in for a renal ultrasound-everything was fine with my kidneys but put me on more antibiotics. The pain started to go away after taking them. I started to wonder if it could be an std. I have been with the same man for 2 years and was tested negative for chlamydia and gonorrhea after around 6 months after we started having sex.( He swears up and down he never cheated and said if I somehow got an Std that I could literally do anything for revenge.) Today i went for a follow up and he said the burning could be caused because my urine is very alkaline and I should eat more meat to make it more acidic. But what doesn't make sense to me is that there were a few white blood cells but no infection found and i was having pain, but no uti. And, sense there is no infection why did the antibiotics seem to help? I told the doctor I was sexually active when he asked, but has never suggested being tested for std's, is this because these aren't symptoms of an std, or is it because he is trying to stay within the field of urology and not gyno?