I often hear the question of does a narcissist cheat? or why do narcissists cheat? what is cheating to you or i is different with a narcissist because they have no commitment in their sick little minds, so spreading the love is really just "getting supply". They have shown you signs and you might have missed them or you might have listened to their pathetihic excuses, or if you really have a gem of a narcissist he probably blamed you for them cheating!!! THIS IS NEVER EVER TRUE - a narcissist cheats to always keep new supply in the wings. learn how to recognize the signs and how to protect yourself.
WEBSITE - resources for victims - http://narcissistabusesupport.com