When you're in a relationship with a narcissist, there will always be another secret life going on behind your back.
This is because these people are very empty, and they need stimulation from multiple sources just to face existence. They'll be doing drugs or pornography. They'll be stringing multiple partners through flirting and emotional affairs. They will be chasing financial intrigue that occasionally gets them into scams and trouble.
The reason they must flirt with other people is also because they're seeking to move on to other people who don't know the games they play.
They know they'll get bored with you eventually, or you'll learn to resist their shenanigans. And since being alone would kill them, they begin to groom possible replacements among anyone whom they can charm.
You'll also notice this habit of making promises to you and then using those promises as a dangling carrot to get compliance from you. If you don't do what they want, they'll withdraw the promise.
Sometimes, they'll deny having promised at all, or they postpone it until you give up. The truth is that they never intended to fulfill it in the first place.
Narcissists have lost all sense of right and wrong. Everything is about satisfying themselves.
When you finally leave, they'll circle back to you, pretending to be checking on you when actually they're checking if they still have access.
If you have a child with them, they would weaponise that child to torture you until you cut them off totally or you manage to enforce boundaries with the help of the law.
But the child will be scarred or wasted by the counter parenting and objectification from the narcissist.
Society knows very little about narcissists.
Sometimes, you stay because you fear the pain of letting go until you realize the pain you're already taking for holding on.
Other times, you think you're staying for the children until you realize that the narcissist is turning all of them into other small narcissists and broken empaths.
Your solution is to recognize that this person is incapable of peace. They're only excellent at pretending and confusing you.
You will never have a life until you detach from them and direct your life towards wholeness and emotional stability.