Let me share a story about my best friend and her five year old newly circumsised son. He got four UTI's in his life. Two of them were when he was a toddler, the other two were two months apart when he was five. The doctor suggested that she circ him. She didn't want to, but hated that he kept getting infections. So, she went along with it. So, they circ'ed him, and while he was healing from the circ he got another UTI (Can you imagine how painful that was?), they cleared it up, and three months later he got another one. Now just yesterday she calls me and tells me he HAS ANOTHER UTI!!! Now, circ'ing did nothing for his UTI's. In fact, I think it has made them worse. A lot worse!! Don't get him circ'ed you will regret it if he still continues to get UTI's.
What I wanted to add in is, the fear I feel for other parents and their son (s) under the OP doctor's "care". Since most often think, "She's the doctor, and we're not. Okay. We don't want to, but we'll do it because it's your 'expert' opinion." and it's the parents who... tragically... get final consent!!!
I'm so glad for your son's sake, and the many people throughout his life your intact son can positively influence by having you question authority and look in depth to it!