secret pregnancy

So as some of you may know we're dealing with DCFS for our first son and I'm currently almost 20 weeks pregnant....everyone on DH side knows and everyone where we live knows my dad knows, however I still have to tell my mom and I'm terrified to tell her because I have no idea how she'll react to the news. But I know I can't keep putting it off....any advice on how to tell her? She lives in another state so we don't see each other and only talk over the phone, but she is talking about coming up this fall and I'm just terrified telling her I'm pregnant again is going to make our Rocky relationship even worse....any words of wisdom or advice?