My ds has just turned two. A few weeks ago he seemed to be making a strange grunting noise when urinating. We took his nappy off and he didn't urinate for over 4 hours despite trying all the usual tricks. Eventually he went when he was asleep. We tested his urine no signs of infection. The past few nights he hasn't urinated for over 13 hours when asleep. Despite waking up for a drink and drinking 10 oz of water. His nappy is bone dry. This is unusual for him as 99% of the time his nappy is bulging. After an hour of being awake he eventually goes so much that his nappy is leaking. Slightly worried that somethings going on. 