I'm really sorry that you didn't hear 'Boy' and that your DH and family are being jackasses. Your DH's behavior is especially uncalled for. Keep reminding him that he ASKED for another child knowing that there was no guarantee that it would be a particular gender. Maybe you can agree on color gender neutral for the nursery? My friends painted their baby girl's room light green. I would tell him that keeping the room blue will only serve as a painful reminder to you both of what you don't have.
I can tell you that as much as I was devastated to have not get a boy last time
around, that it's really fun dressing my girls in matching outfits. I really hope that things get better for you and that everyone's attitude changes as they bond with your little girl.