B.S.
This may sound silly, but try going up a size in diapers, and put them on so that the bulk of the diaper is in the front. Maybe that will get him through the night. This is in addition to what the other mommies may suggest about cutting off any fluid an hour before bedtime. I know it is very young, but anytime they are frustrated with a wet/dirty diaper, potty training is easier. Just something to think about...