My sister is pregnant and I can’t find it in me to be happy.

So my younger sister just told me she is having a baby and as she was telling me I was holding back tears with everything I’ve had inside me. I tried to be happy for her but I’m sure the disappointment showed on my face. I haven’t talked to her since, or showed any type of excitement. My SO and I have been trying for a year and this just feels like a huge slap in the face from God. I am trying so hard to keep my feelings to myself but damn it’s hard. I don’t want to feel this way, I want to be happy. I feel like an awful person for not being happy. It feels like everyone but me is getting pregnant and I don’t know how much more I can take the disappointment of every month not getting a BFP. Please tell me I’m not selfish or crazy for feeling this way? I need some support and I can’t get that from my family right now.