To dream that you are cheating on your spouse, mate, or significant other, suggests feelings of self-guilt and self-betrayal. You may have compromised your beliefs or integrity and/or wasting your energy and time on fruitless endeavours. Alternatively, it reflects the intensity of your sexual passion and exploring areas of your sexuality. It is a reaffirmation of your commitment. To dream that your mate, spouse, or significant other is cheating on you, indicates your fears of being abandoned. You may feel a lack of attention in the relationship. Alternatively, you may feel that you are not measuring up to the expectations of others. This notion may stem from issues of trust or self-esteem.
Dreaming that you are having sex with someone other than your partner may mean several things. Again, since everything in dreams is symbolic, including sex, the sex act itself must be interpreted using the lens of symbolism. Sex in dreams often means unity - becoming one with something. In a dream, this unity may be expressed by sexual union with someone who is symbolic of something important to you. For example, if you dreamed you were cheating with someone famous, it could mean that you desire more recognition or it could mean that you are giving yourself the recognition and value you deserve. Look at who you are having sex with and what they represent to you - this is a huge step in discovering what the dream itself means.
Dreams of cheating may also be dreams of wish-fulfillment. Perhaps you have become infatuated with a person outside of the relationship. Dreams of sleeping with that person are ways that one can have the experience without the devastating consequences! If you continue having dreams of this sort, look at your relationship and see if your sex life is lacking. Talk with your partner and see if there are ways in which you can improve your sex life.