When is it going to be my turn

So I found out the other day that my sister who has 2 grown children is about 7 weeks pregnant... While my husband and I are over here going on 7 years of trying to get pregnant. I'm happy for her, truly I am, but does it make a selfish/bad person to be upset/depressed at the same time? Like when is it going to be my turn? I just want to cry myself to sleep but scream at the same time.