Advice please!

Luna • 1.15.12
Hey everyone! 
 My name is Luna, I'm a 20 year old from Miami and I need a bit of advice. Here is some backstory: me and my parents don't have the best history. Because of the mistreatment over the years, this past May I decided to leave my house. It was childish and I hated the way I left (packing that night and leaving a note), but I had to leave because it wasn't a healthy environment.  Anyway, I currently live with my boyfriend (of 7 years) and his parents. I've been so grateful to them taking me in! Over the last couple of months, I've been out with my parents and my younger sisters and over my old house a couple times and things have been great. But now with the news of telling everyone that I'm pregnant, I'm worried that the relationships between both my parents and his, will be compromised. My parents are somewhat obsessed with "family image" and they are very involved with the local Catholic Church. With this parents I am scared that they'll kick us out. To further complicate things with this parents, turns out we are following in their footsteps. When his parents were 18, his mother got pregnant, the fathers parents kicked him out upon hearing the news and he moved in with her family.
What I'm asking is how do I tell them? I realize this is a serious matter so I can't do any of the cute announcements I would love to do from Pinterest but I have no clue how to approach this. 
Any help and advice would be greatly appreciated :) thanks so much everyone!