Poo in the potty

Oliver will be turning 3 years old next month and he certainly hit new milestone just a month ahead. He finally poo in the potty after months of Boon Heng trying to coax him into using the potty. At home, Oliver goes without diaper. Now we cut down his milk feed to only two rounds (240 ml per feed), Oliver seems not to pass urine frequent enough. I am worried that he holds back which will lead to another round of urinary tract infection. Other than my undue concern, our attempt to go diaperless is rather successful.