Hi -
I merged your duplicate post from the Bloodhound area since it was the very same post as this one.
I also had to change the subject of your post as it did not tell anyone what your posted about - it said questions needing answers. You'll grab more attention if you use subjects that are clear and specific.
Anywho, welcome.

A few thoughts.
Why buy a Doberman from a pet store? Why not save a life of one that is in a Doberman rescue? Pet store Dobermans tend to come from horrible puppy mills. Buying from the store supports that trade.
If you are set on buying look for reputable breeders that you can visit that breed for health and temperament, not volume cheap sales. Buying from a breeder is not bad, just don't support puppy mills. Without quality breeders breeds would disappear. But you want to see the conditions your new dog comes from. You can't do that with a pet store dog.
If you have young dog (the bloodhound) and are pregnant, I don't pretend to tell you your business but is this the time to bring another handful into the house?
Dobermans are very high energy dogs. Can you provide the exercise and attention a young Dobie requires? If not chaos could ensue.
I don't think there is anything in either breed that makes them incompatible to live in the same house. Both the Bloodhound and the Doberman will look to you and the other humans for leadership about how to act - it is all up to you, not the breeds. You must train and exercise both and establish the pecking order (pack hierarchy).
If you can do that, the breed does not matter. And don't forget, every dog is an individual. Don't assume every Dobie is the same as every other.
Please consider waiting until things are quiet in your household and if you go forward, please consider adoption from a rescue instead of the pet store puppy mill dog. Good luck and keep us informed as to how things are going.