Rose tinted glasses.
He is a liar. Where does his wife (and the child he can't lose) think he is every time he is off meeting you for a sordid shag?
He diverts energy and emotion from his family. He could be spending time with this child that is so precious to him that he won't leave but no his dick is more important. Who do you think is at home looking after his child and doing all the house stuff while he is off meeting you for a sordid shag?
Who do you think is washing and ironing all those clothes he pulls off and dumps on your floor when he meets you for a sordid shag? Bet it isn't him... Think of that the next time you help take his clothes off. Some poor unknowing woman made them nice for you to do so.
He is risking his partner's sexual health. She has no choice in this, she doesn't have a clue that he is off meeting you for a sordid shag.
Where do you go for these sordid shags? Does he ever take you away to hotels? Use money that could be spent on that precious child he won't leave you for? Or does he just come to yours, use your facilities for a sordid shag and then go home to his wife?
Does he take you for meals? Buy you presents? I wonder if like loads of the cheated on partners on here his wife is scrimping and going without to provide for his much loved child so that he can do things with you.
Tried to go no contact? Please don't bullshit us even if you are bullshitting yourself. The desperate no contact for a few days is the sop to your (and his) conscience so that you can say you 'tried'. Meaningless shit as you know you will be back in contact in a few days as it is meant to be and beyond sex 
No one can help you. You chose this. The only one who can end it is you. As long as you continue with the beyond sex bullshit you will not stop.