We were in the exact same situation as you with our second son. He was on his 4th UTI and had been on prophylactic antibiotics for 3 1/2 months (and he was only 4 months old). LIke your son, the tests for kidney reflux came back clear, but he kept getting infections. We decided to go ahead with circumcision. My son is now almost 4, and we have not had another UTI since. It was a difficult decision to make, especially as our older son was not circumcised, and they are now different to each other, but ultimately we needed to try it because he was just so sick and was getting more and more resistant to the antibiotics. He was losing weight, and not thriving. Best decision we ever made. Good luck with yours.