My DH has had a really hard time, too. TBH, I think he went through a few phases -- when LO was first born, it was all new and kinda cool. DH got a bit of extra attention from others as a "new daddy." That last about 2 weeks.
Then he realized how much of MY time LO took -- how LO's needs always came first. How I was always on DH's case to be more aware of how what he did affected the baby (e.g. stop making so much noise when you come through the door! You are waking the baby that I JUST got to sleep!
)
This made him start to resent the baby. Also, he had a terrible time trying to figure out how to soothe and comfort LO. So LO would always cry when DH held him and DH couldn't make him stop. It was all very frustrating for DH. I think he felt like a crap father to a son who had stolen his wife away.
That lasted a couple of months. JUST when I was at my wits' end and starting to worry about their bonding... LO got more interactive. He started to smile and giggle and play more. He got a bit bigger and "tougher" and would interact with DH more. DH was able to start to help LO practice sitting, standing, and rolling.
Then, the magic day, at about 4.5 months old, when LO laughed... really laughed... JUST for DH for the first time. I finally saw happy tears in DH's eyes and it has been much better since. Now, DH comes in the door and wants LO first thing -- who is all smiles for his Daddy.
ok, that was long!
My point -- it will get better. Try to encourage bonding when you can, but try not to force it. It will come when they are ready.