Losing hope

We’ve been having unprotected sex for about a year and a half and nothing seems to happen no matter how much I plan for it 😞. My sister got pregnant with in the first month they tried and she even ended up with twins! I was happy for her but my heart was crushed because she has a 2 yr old who she struggles with due to the baby daddy not helping her. And now she’s been blessed with twins 🥺. I feel so bad for being jealous but I can’t help it.