Firstly congratulations on your much wanted pregnancy. I'm sorry that you are feeling so sad, this should be an exciting time for you and DH but it's not.
I think there he might be feeling a little torn and confused at the moment. I remember being pregnant with my second and thinking omg what have I done to DS? Almost like I betrayed him by having another baby. Until I realised that I was actually giving him the greatest gift of all, a sibling. Maybe DH feels similar? Like at the moment he sees his amount if love as finite rather than infinite, that is there is enough to go around for dsd and the new bub? And yes he's probably carrying some guilt over the way he raised his dd.
Have you tried discussing what is behind these feelings? I'm assuming he wanted this baby as much as you did, I wonder what's changed since you've actually become pregnant?