Eeny, poor you, it sounds as though you have been through a lot, and haven't had a chance to deal with it all yet.
I have an idea, at least, of the fear and foreboding about something happening to your baby. While nothing has happened that close to me, there are an awful lot of dead children in my family, and I was convinced, every night for the first year at least of dds life, that I would wake up in the morning and she would be dead. Your brain does make all sorts of irrational deals and connections, and won't be reasoned with sometimes. And has hatjam says, it does wear off, in the end.
Perhaps, as someone else said further up, it might help to face up to the dreams. Keep an dream diary - if you can, write them down as soon as you wake. That in itself can often help to change them. But if that doesn't work, take a good look at the dream. Some people think that every single important figure in a dream is a part of you. So write down what all of the people/animals/things in your dream have to say. You might be surprised what you find, and it can definitely help to take the power out of the dream.
And pregnancy gave me the most lurid and fearful dreams - probably the hormones mixed with a memory of all the dead children who came before - so that might be something to do with it too.