Advice on in laws.

So, my living situation isnt the greatest. I live with my in laws with my fiance and our 2 yr old. Found out im pregnant again. Idk how they are gonna take this. Im scared to tell them. My fiance has joked with her and her responses werent so great, like youll be kicked out, shed beat him and etc. His dad ive heard diff stories. Of happy and mad. We both work, we just cant afford our own home atm. I dont know how to tell them and i dont want them to just figure it out. Or should i? My mother on the other hand she will be able to tell eventually. Lol and advice please?? Me and his mother have moments but do get along.