I am so sorry hun for all that you've been through. Your natural instinctive reaction is going to be just what it is. You are trying to protect yourself. But, come a time, you should also let yourself enjoy it while it's there. I tell myself that I need to live in the moment for now. Now, that doesn't necessarily mean go buy a bunch of baby stuff. But I am slowly letting myself "like" being pregnant. I think after a loss, all of us ladies can say that the joy just wasn't there like it was the first time when we became newly pregnant.
Whatever happens with this pregnancy will be emotional, it can be a high or a low at different times. God forbid if anything were to happen the only reaction will be devastation whether you were "connected" or not. And I know that what you've been through gives you the right to not want to get attached, but I think you should really start allowing yourself some love, in whichever way that may be.
I hope I have helped you in some way, and by mentioning loss above^ I hope I haven't scared you, I just wanted to make a point. I pray that your baby is safe and sound and that this is your forever rainbow baby.