Cheating

I feel like I should walk away. I love him but cheating is not acceptable. I hate that I found out and he says that I always was the one he wanted and still want. He became best friend with his coworker and we were in a big fight one day he asked her help on how to fix it even though she knew we were in bad terms. So she decided to go down on him he pushed her away and ever since then she was pushing on him and she threatened him she will tell me what had happened so he did what she wanted to sleep with him now I just can't forgive him. I can't say I love him anymore sex is not the same we have no connection whatsoever is like I am laying there so he can finish. We have kids together which makes me not want to leave him but deep inside I want to. How can he love me and still cheat? How can he do this to our family?