Sounds like he has reached the age when he really knows who his mummy is! Both my boys have done this. I think it has to do with your smell too, he most likely smells your milk when he is with you and it calms him down. I would say it is definitely related to the arsenic hour.

It's hard for your DH not to take it personally, I'm sure most dads feel the same way, but it is just a phase that will soon pass. Once he starts getting more animated and recognising his daddy he will be happier to go to him. It will happen soon, I promise!