Dreaming about adultery indicates you are not happy with the relationship and commitment you are in. You are seeking the excitement you have lost due to the familiarity of living with a person for too long, and the urges to have an affair is your way of betraying the person you are currently with.
When it is someone in your life committing adultery, then it means that you are insecure and fear being cheated on. It could be a simple misunderstanding where they are paying you a little less attention due to work load or heighten stress levels.