I just don't know

So about a month ago my mom(40) told my sister(14) and I (22) that she's pregnant. When people ask me how I feel about it I honestly don't know what answer to give them because I don't even know how I feel. I mean it's a baby so yes that's a blessing..but at the same time I'm kind of annoyed I guess that I'm so old as a big sister, and that they are also going to be grandparents soon so why try having a baby? I don't know, I feel horrible for even feeling bad about it at all. What's wrong with me!? 😞