Staying dry for periods of time during the day (daytime continence) is usually achieved between 36 and 48 months of age, with nighttime continence coming months to years after that. By meeting with your child's doctor, you can assess your child's signs of readiness for toilet training and identify potential barriers that may be slowing his progress.
There are many reasons why a child may be resistant to toilet training -- stress in the home, illness, hard stools, and parental pressures are common causes. The key for parents who are dealing with a resistant child is to stay positive and to reinforce all signs of progress. Sometimes a child even benefits from taking a break from toilet training. The "time off" can be helpful in decreasing the pressure of the experience for both parent and child. Talk with your pediatrician for the right approach for your son.