I suspect this is bothering your son just as much, so together success can hopefully be achieved. Once your child is interested in overcoming his bedwetting, two guiding principles apply: work with him and protect his self esteem. A child has to learn either to sense a full bladder during sleep and contract the muscles which hold in urine, or to wake from sleep, find the bathroom, and pee in the toilet. No small task for the average five-year-old!
Discuss specific training methods with your pediatrician. Initially the goal is getting up at night and using the toilet. Discontinue diapers or pull-ups. Use a plastic mattress cover. Enlist your child's help in cleaning up and changing the bed. Avoid punishing or criticizing. Limiting fluids may not have much of an impact. One successful method uses an alarm, which is set off when a sensor, worn in the underwear, gets wet. Medicines are used only in special circumstances. Whatever your method, be patient and plan on keeping in close contact with the pediatrician for guidance and reassurance.