He does not seem excited to get intimate with you, it feels like more of a duty
He is asking for too much space, which is unnecessary and does not make any sense.
He stops putting in effort, you are the only one giving in efforts and carrying the relationship.
If you have found out your partner has cheated on you, and not just once, but there are more instances than one, then this is his way of silently letting you know that he wants out.
Maybe in the heat of the moment, he has slipped it. It could be something like he is still with you because of some obligations or because of the kids.