Narcissist are broken and want to break you.

Narcissist are broken mentally and emotionally. You made them feel amazing for a certain period of time obviously that time is over since you are asking this question.

Narcissist  fear abandonment so deeply that they could leave you for someone else and be so hurt that you moved on and are dating again.

The reason to make you suffer is because they are the ones suffering worse then you ever could. 

 But this the only way they know how to function. 

So by punishing you they are desperate for a reaction good or bad makes no difference to them as it is attention and shows they still have control.

Ignoring them causes a HUGE blow to their ego and they HATE it! It EATS them ALIVE!

They will abuse the new supply or smear you to their friends and family to try and maintain control over their own emotions since YOU wont give them what they want.

Seeing you hurt give the narcissist power!

 Seeing you happy makes them ANGRY!

Narcissist Thrive on Emotional Reactions

Narcissist thrive on evoking both reactions and emotions from their victims.

The narcissist wants you to respond to their unrealistic demands. They are aware of what they are doing, that's exactly why they do it. When the narcissist isn't treating you like garbage or like your existence is irrelevant, they will be doing or saying things to cause you pain. Most victims do not understand the person they are in love with lacks the ability to Love them back. They believe they are to blame. They do not understand why they are being rejected.  So they keep trying to please.  
The narcissist sees this as weakness and continues to allow their victim to be in pain, by rejecting them, cheating on them, and lying to them. 

It is hard to get through to the narcissists victim at this time. But eventually the victim will have enough. Unfortunately by the time the victim realizes this, they have been beaten down 
emotionally. They are depleted of energy and hope. It usually can take the victim years to 
get over their ordeal with the narcissist. And in all truth, the abuse they suffered cannot be forgotten. 

Don't lose hope if this is you. Once you have gotten the narcissist out of your life. Begin to LIVE again. Focus on healing your mind, body, and soul.