Encouragement needed😔

So me and my sister in law have been ttc for the same amount of time, we found out she's 3 months pregnant. I'm am happy for her it I'm very upset and down. My husband is jumping for joy that he will be an uncle and I don't want to tell him how sad I truly am, he asks what's wrong and I just say nothing. I don't know what to do, or say or feel.😔