G.M.
The same thing happend with my daughter. An ulrasound revealed compacted poop in her rectum and that would prevent the emptying of the bladder, so then when she slept, the bladder would trickle out all night long. The doctor put her on Miralax and a high fiber diet so she can poop better and not wet the bed anymore. We now use pull ups to sleep, travel, etc. Take him to the doctor and have an ultra sound done!