don't want to tell family I'm pregnant

Mo • Married 9/24/16. Mommy 7/22/17 ❤️
I've been really excited lately about planning how to tell my mom and my husbands parents that we're expecting. 
When I was 18 I had a son and I placed him for adoption. My husband is not the father - it was some other jerk or cheated on me and neglected me and my husband (at the time just friend) picked up the pieces and cared for me. He even came to the hospital after I gave birth and held my son. We never really talk about it - per my request. It was the worst time in my life  
Now 4 years later we live on our own, we're married and are having a baby! We're super excited and have been looking forward to this for a while now. But I don't want to tell people who know about my previous pregnancy because I know they'll bring it up!! I DONT WANT TO TALK ABOUT IT. I only want this baby and this pregnancy to be discussed. I don't want anyone to bring it up but my family is super insensitive and don't respect my wishes at all. 
My husband gets really sad when people bring it up, he hated seeing me go through that and he probably hates the idea that I had a child before him and now this is my second baby and only his first. 
How do I tell people without them bringing it up! People act like they can just say whatever the fuck they want and if someone brings it up I will get so upset and probably yell at them and then feel super uncomfortable. I don't know what to do and I don't want anyone to make you husband and I drudge up bad memories.