I had the same problem with my son! He wears size 3, so I tried a size 4, but that didn't work - they were just too big. I finally got tired of washing and changing sheets and pjs every single morning, so I broke down and bought the Huggies night time diapers. The smallest they have is size 4, but they work great at night! I don't have the problem anymore. They are expensive, but one pack lasts a long time. I also tried cutting back his liquids an hour or so before bed, but that didn't help much, and I hated turning him down if he got thirsty. The night diapers are the way to go, at least for my son.