Hey - you'll always get lots of advice from everyone here at CAC!
I hope you aren't feeling too overwhelmed...lots of very good advice from the previous posters.
When I was younger, I had TONS of UTIs - so many, in fact, that I was admitted to hospital for 'exploratory surgery' to see if I had some kind of structural abnormality.
I didn't - I was just very prone to UTIs as a young child. This was something I eventually outgrew - probably by around 8-9 years old, I think.
I do remember, though, that I was never allowed to use bubble bath, as that would always trigger another UTI. I know with my intact son, All I ever get him to do is swish his penis around in the bath (he's 4 years old now) - he's never had any problems. When he was an infant, I just wiped it down like a finger after big blow-out diapers, and that was it.
I would second (or third) the recommendation to get a new doctor. Or at the very least, tell your current doctor that (as someone else posted), he/she needs to treat your son in the same way he would treat a girl who presented with a second (or third) UTI.
Good luck...I hope you can get this cleared up sooner rather than later.