might just be a case of time ....... will take time for your little man to adjust to a new routine with his daddy but he will get it! maybe any chance your DH gets, get him to settle your DS and initially it might seem painful but don't go in! Leave it to your DH otherwise your little one will learn that eventually mummy does come in anyway. So make yourself a cup of tea and heap loads of encouragement on your DH as he will need the support too as it may be just as taxing for him! Persistence will pay off (both my girls have gone through the same thing so I understand! It does get better! )

hth lovey and good luck!!