Does it make me a bad person?

Lea

Me and my boyfriend have been ttc for 3 and a half years and I'm not pregnant. My sister has been trying for only a couple of months and she just got pregnant. I'm happy for them... but I'm also a tad bitter. This would be the first grandchild in our family and I thought it would be me.. I feel horrible.. I don't get why it's never me..