To see or wear a diaper in your dream symbolises your childish or babyish attitudes/actions. You may be too dependent on others.
To dream that you are changing diapers suggests a need to clean up you behavior and change your childish ways. Perhaps you need to change your attitude and approach regarding a new idea or project.
To see dirty diapers in your dream indicate that you need to clean up the mess you have created as a result of your childishness.