Dreaming about being unfaithful suggests that you take a better look at your current relationship.
What was the person in your dream giving you (emotionally or otherwise) that your real life partner does not?
Communicate effectively and begin to develop those areas of your relationship that need most improvement.
Understanding this dream may assist you in understanding your relationship and the level of attachment to your partner.
In either case, they are upset and outraged by such dreams.
It seems logical that these types of dreams are connected to feelings of inadequacy or dissatisfaction.
If the partner in your dream was a total stranger then the dream may be much more personal and profound.
If you dream of cheating in any manner, either by you, or by your loved one, then this is a direct warning for you to be more circumspect about your actions to and with the opposite sex.
It is warning you that if you do not, you will suffer the consequences.
If you are the cheater in your dream, you may have a guilty conscious about cheating that has nothing to do with love.