Like some of the best I ever had.

that was the best night I have ever had.

like I have no feelings for this new girl other than the fact that I really want to see her again and again.

sleeping with random girl I meet that gave me the best night I have ever had till this day.

...

You do have feelings for her, and you are continuously reiterating and conditioning yourself to have more feelings for her.

Every romantic relationship is based on a sexual component, if the sex is good the potential for romantic feelings is nearly guaranteed.

That, and you continually seeing her, along it being something you're not supposed to be doing, you're going to be emotionally involved in this for a while.

Did your wife take on the mother role too hard? That's usually how it starts. Then you lose sexual attraction for her, etc. She probably has already cheated on you and you feel inadequate in some way, but maybe not. I'm only spit-balling here.

Either way, you could pull out now before the other woman starts acting on the feelings she has for you. And that is going to be a hell of a lot worse, when she starts wanting to blackmail and extort you into staying with her.

I'm glad you enjoyed the sex though. Cheating is fun.