Worried? Yeah I am.

I have a 3 year old son who's father wanted/wants nothing to do with him. Fine by me. I'm currently pregnant with another man's baby and we are NOT together and I'm trying hard to keep him out of my baby's life as much as possible because he is abysive and has a sex addiction among violence and other things. BUT, how if he gets to see this baby and do things and buy gifts for it and what not, how am I going to explain to my 3 year old that this baby has a daddy and he doesn't? What about when him and his family buy the baby stuff and what not and don't do nothing for my son? I'm so worried about this. That's its going to hurt my son on so many levels and that it'll make him resent this baby. I can't tell you how many times I've just wanted this pregnancy to end. Because my world is a mess since losing my mom. And this makes everything in the world even worse. I love my baby, I do. But I don't want this baby to endure the abuse that I and my son have had to go through with this psycho. So please give me ideas because the courts will more than likely give him supervised visitation to this baby at some point and I want to be prepared on how to handle it all. Thanks!