WAS NOT EXPECTING THIS

So my mother in law is about to be 50. I am 23 and ttc but it's only been 6 months so I'm not too too worried right now. my mil has had 5 kids, but one passed from SIDS at 2 months old. Her oldest is 30 and her youngest is 22. She's not the healthiest but she tries and she doesn't get much exercise because she's had a stroke a couple years ago so we try our hardest to get her moving when we can. I honestly have a great relationship with her and am always trying to do what I can with her (like learning how to cook some of my bfs favorite dishes and learning spanish) Well the other day she was saying she felt sick and nauseated and bloated. I had just gotten over the flu and I had mistaken a lot of the symptoms for pregnancy so I was sad when the doc said no. That was a few days ago and I confided in her telling her how I couldn't wait for my day. Well today she couldn't take it anymore and asked me to take her to the ER bc she had thrown up and was nervous it was another stroke. So I rushed her there and they said it sounded like the flu. They did blood work and when they came back, they told her she appeared to be pregnant. Sure enough, they did a sonogram and bam! BABY! We all are so shocked and my bf is happy but weirded out to have a new baby bro or sister. I'm happy for her as she is, but it made my depression flare up and I feel selfish. I don't want to make the situation about me so I haven't told my bf yet, but I feel kind of empty now. Anyone else had this happen? How did you cope?