Feeling a little down :/

I received a phone call from my sister in law today she had a positive pregnancy test. I'm excited for them and I can't wait to be an aunt but at the same time I did get a little upset because my husband and I have been TTC for a while now and it this marks the 6 person so far that I know that has become pregnant. I feel horrible for being upset I feel like this makes me a bad person. How can I be excited for them and be upset at the same time???